diff --git a/docs/changes/newsfragments/161.feature b/docs/changes/newsfragments/161.feature
new file mode 100644
index 0000000000..6c1e3742e5
--- /dev/null
+++ b/docs/changes/newsfragments/161.feature
@@ -0,0 +1 @@
+Introduce :class:`.Smoothing` for smoothing / blurring images as a preprocessing step by `Synchon Mandal`_
diff --git a/junifer/preprocess/__init__.py b/junifer/preprocess/__init__.py
index 15042f0eec..d60c6efddb 100644
--- a/junifer/preprocess/__init__.py
+++ b/junifer/preprocess/__init__.py
@@ -9,3 +9,4 @@
 from .confounds import fMRIPrepConfoundRemover
 from .bold_warper import BOLDWarper
 from .warping import SpaceWarper
+from .smoothing import Smoothing
diff --git a/junifer/preprocess/smoothing/__init__.py b/junifer/preprocess/smoothing/__init__.py
new file mode 100644
index 0000000000..0236a63d1e
--- /dev/null
+++ b/junifer/preprocess/smoothing/__init__.py
@@ -0,0 +1,6 @@
+"""Provide imports for smoothing sub-package."""
+
+# Authors: Synchon Mandal <s.mandal@fz-juelich.de>
+# License: AGPL
+
+from .smoothing import Smoothing
diff --git a/junifer/preprocess/smoothing/_afni_smoothing.py b/junifer/preprocess/smoothing/_afni_smoothing.py
new file mode 100644
index 0000000000..50fd27161b
--- /dev/null
+++ b/junifer/preprocess/smoothing/_afni_smoothing.py
@@ -0,0 +1,119 @@
+"""Provide class for smoothing via AFNI."""
+
+# Authors: Synchon Mandal <s.mandal@fz-juelich.de>
+# License: AGPL
+
+from typing import (
+    TYPE_CHECKING,
+    ClassVar,
+    Dict,
+    List,
+    Set,
+    Union,
+)
+
+import nibabel as nib
+
+from ...pipeline import WorkDirManager
+from ...utils import logger, run_ext_cmd
+
+
+if TYPE_CHECKING:
+    from nibabel import Nifti1Image
+
+
+__all__ = ["AFNISmoothing"]
+
+
+class AFNISmoothing:
+    """Class for smoothing via AFNI.
+
+    This class uses AFNI's 3dBlurToFWHM.
+
+    """
+
+    _EXT_DEPENDENCIES: ClassVar[List[Dict[str, Union[str, List[str]]]]] = [
+        {
+            "name": "afni",
+            "commands": ["3dBlurToFWHM"],
+        },
+    ]
+
+    _DEPENDENCIES: ClassVar[Set[str]] = {"nibabel"}
+
+    def preprocess(
+        self,
+        data: "Nifti1Image",
+        fwhm: Union[int, float],
+    ) -> "Nifti1Image":
+        """Preprocess using AFNI.
+
+        Parameters
+        ----------
+        data : Niimg-like object
+            Image(s) to preprocess.
+        fwhm : int or float
+            Smooth until the value. AFNI estimates the smoothing and then
+            applies smoothing to reach ``fwhm``.
+
+        Returns
+        -------
+        Niimg-like object
+            The preprocessed image(s).
+
+        Notes
+        -----
+        For more information on ``3dBlurToFWHM``, check:
+        https://afni.nimh.nih.gov/pub/dist/doc/program_help/3dBlurToFWHM.html
+
+        As the process also depends on the conversion of AFNI files to NIfTI
+        via AFNI's ``3dAFNItoNIFTI``, the help for that can be found at:
+        https://afni.nimh.nih.gov/pub/dist/doc/program_help/3dAFNItoNIFTI.html
+
+        """
+        logger.info("Smoothing using AFNI")
+
+        # Create component-scoped tempdir
+        tempdir = WorkDirManager().get_tempdir(prefix="afni_smoothing")
+
+        # Save target data to a component-scoped tempfile
+        nifti_in_file_path = tempdir / "input.nii"  # needs to be .nii
+        nib.save(data, nifti_in_file_path)
+
+        # Set 3dBlurToFWHM command
+        blur_out_path_prefix = tempdir / "blur"
+        blur_cmd = [
+            "3dBlurToFWHM",
+            f"-input {nifti_in_file_path.resolve()}",
+            f"-prefix {blur_out_path_prefix.resolve()}",
+            "-automask",
+            f"-FWHM {fwhm}",
+        ]
+        # Call 3dBlurToFWHM
+        run_ext_cmd(name="3dBlurToFWHM", cmd=blur_cmd)
+
+        # Create element-scoped tempdir so that the blurred output is
+        # available later as nibabel stores file path reference for
+        # loading on computation
+        element_tempdir = WorkDirManager().get_element_tempdir(
+            prefix="afni_blur"
+        )
+        # Convert afni to nifti
+        blur_afni_to_nifti_out_path = (
+            element_tempdir / "output.nii"  # needs to be .nii
+        )
+        convert_cmd = [
+            "3dAFNItoNIFTI",
+            f"-prefix {blur_afni_to_nifti_out_path.resolve()}",
+            f"{blur_out_path_prefix}+tlrc.BRIK",
+        ]
+        # Call 3dAFNItoNIFTI
+        run_ext_cmd(name="3dAFNItoNIFTI", cmd=convert_cmd)
+
+        # Load nifti
+        output_data = nib.load(blur_afni_to_nifti_out_path)
+
+        # Delete tempdir
+        WorkDirManager().delete_tempdir(tempdir)
+
+        return output_data  # type: ignore
diff --git a/junifer/preprocess/smoothing/_fsl_smoothing.py b/junifer/preprocess/smoothing/_fsl_smoothing.py
new file mode 100644
index 0000000000..2e02ea2226
--- /dev/null
+++ b/junifer/preprocess/smoothing/_fsl_smoothing.py
@@ -0,0 +1,116 @@
+"""Provide class for smoothing via FSL."""
+
+# Authors: Synchon Mandal <s.mandal@fz-juelich.de>
+# License: AGPL
+
+from typing import (
+    TYPE_CHECKING,
+    ClassVar,
+    Dict,
+    List,
+    Set,
+    Union,
+)
+
+import nibabel as nib
+
+from ...pipeline import WorkDirManager
+from ...utils import logger, run_ext_cmd
+
+
+if TYPE_CHECKING:
+    from nibabel import Nifti1Image
+
+
+__all__ = ["FSLSmoothing"]
+
+
+class FSLSmoothing:
+    """Class for smoothing via FSL.
+
+    This class uses FSL's susan.
+
+    """
+
+    _EXT_DEPENDENCIES: ClassVar[List[Dict[str, Union[str, List[str]]]]] = [
+        {
+            "name": "fsl",
+            "commands": ["susan"],
+        },
+    ]
+
+    _DEPENDENCIES: ClassVar[Set[str]] = {"nibabel"}
+
+    def preprocess(
+        self,
+        data: "Nifti1Image",
+        brightness_threshold: float,
+        fwhm: float,
+    ) -> "Nifti1Image":
+        """Preprocess using FSL.
+
+        Parameters
+        ----------
+        data : Niimg-like object
+            Image(s) to preprocess.
+        brightness_threshold : float
+            Threshold to discriminate between noise and the underlying image.
+            The value should be set greater than the noise level and less than
+            the contrast of the underlying image.
+        fwhm : float
+            Spatial extent of smoothing.
+
+        Returns
+        -------
+        Niimg-like object
+            The preprocessed image(s).
+
+        Notes
+        -----
+        For more information on ``SUSAN``, check [1]_
+
+        References
+        ----------
+        .. [1] Smith, S.M. and Brady, J.M. (1997).
+               SUSAN - a new approach to low level image processing.
+               International Journal of Computer Vision, Volume 23(1),
+               Pages 45-78.
+
+        """
+        logger.info("Smoothing using FSL")
+
+        # Create component-scoped tempdir
+        tempdir = WorkDirManager().get_tempdir(prefix="fsl_smoothing")
+
+        # Save target data to a component-scoped tempfile
+        nifti_in_file_path = tempdir / "input.nii.gz"
+        nib.save(data, nifti_in_file_path)
+
+        # Create element-scoped tempdir so that the output is
+        # available later as nibabel stores file path reference for
+        # loading on computation
+        element_tempdir = WorkDirManager().get_element_tempdir(
+            prefix="fsl_susan"
+        )
+        susan_out_path = element_tempdir / "output.nii.gz"
+        # Set susan command
+        susan_cmd = [
+            "susan",
+            f"{nifti_in_file_path.resolve()}",
+            f"{brightness_threshold}",
+            f"{fwhm}",
+            "3",  # dimension
+            "1",  # use median when no neighbourhood is found
+            "0",  # use input image to find USAN
+            f"{susan_out_path.resolve()}",
+        ]
+        # Call susan
+        run_ext_cmd(name="susan", cmd=susan_cmd)
+
+        # Load nifti
+        output_data = nib.load(susan_out_path)
+
+        # Delete tempdir
+        WorkDirManager().delete_tempdir(tempdir)
+
+        return output_data  # type: ignore
diff --git a/junifer/preprocess/smoothing/_nilearn_smoothing.py b/junifer/preprocess/smoothing/_nilearn_smoothing.py
new file mode 100644
index 0000000000..1ef0498ee0
--- /dev/null
+++ b/junifer/preprocess/smoothing/_nilearn_smoothing.py
@@ -0,0 +1,69 @@
+"""Provide class for smoothing via nilearn."""
+
+# Authors: Synchon Mandal <s.mandal@fz-juelich.de>
+# License: AGPL
+
+from typing import (
+    TYPE_CHECKING,
+    ClassVar,
+    Literal,
+    Set,
+    Union,
+)
+
+from nilearn import image as nimg
+from numpy.typing import ArrayLike
+
+from ...utils import logger
+
+
+if TYPE_CHECKING:
+    from nibabel import Nifti1Image
+
+
+__all__ = ["NilearnSmoothing"]
+
+
+class NilearnSmoothing:
+    """Class for smoothing via nilearn.
+
+    This class uses :func:`nilearn.image.smooth_img` to smooth image(s).
+
+    """
+
+    _DEPENDENCIES: ClassVar[Set[str]] = {"nilearn"}
+
+    def preprocess(
+        self,
+        data: "Nifti1Image",
+        fwhm: Union[int, float, ArrayLike, Literal["fast"], None],
+    ) -> "Nifti1Image":
+        """Preprocess using nilearn.
+
+        Parameters
+        ----------
+        data : Niimg-like object
+            Image(s) to preprocess.
+        fwhm : scalar, ``numpy.ndarray``, tuple or list of scalar, "fast" or \
+               None
+            Smoothing strength, as a full-width at half maximum, in
+            millimeters:
+
+            * If nonzero scalar, width is identical in all 3 directions.
+            * If ``numpy.ndarray``, tuple, or list, it must have 3 elements,
+              giving the FWHM along each axis. If any of the elements is 0 or
+              None, smoothing is not performed along that axis.
+            * If ``"fast"``, a fast smoothing will be performed with a filter
+              ``[0.2, 1, 0.2]`` in each direction and a normalisation to
+              preserve the local average value.
+            * If None, no filtering is performed (useful when just removal of
+              non-finite values is needed).
+
+        Returns
+        -------
+        Niimg-like object
+            The preprocessed image(s).
+
+        """
+        logger.info("Smoothing using nilearn")
+        return nimg.smooth_img(imgs=data, fwhm=fwhm)  # type: ignore
diff --git a/junifer/preprocess/smoothing/smoothing.py b/junifer/preprocess/smoothing/smoothing.py
new file mode 100644
index 0000000000..16f71a3943
--- /dev/null
+++ b/junifer/preprocess/smoothing/smoothing.py
@@ -0,0 +1,174 @@
+"""Provide class for smoothing."""
+
+# Authors: Synchon Mandal <s.mandal@fz-juelich.de>
+# License: AGPL
+
+from typing import Any, ClassVar, Dict, List, Optional, Tuple, Type, Union
+
+from ...api.decorators import register_preprocessor
+from ...utils import logger, raise_error
+from ..base import BasePreprocessor
+from ._afni_smoothing import AFNISmoothing
+from ._fsl_smoothing import FSLSmoothing
+from ._nilearn_smoothing import NilearnSmoothing
+
+
+__all__ = ["Smoothing"]
+
+
+@register_preprocessor
+class Smoothing(BasePreprocessor):
+    """Class for smoothing.
+
+    Parameters
+    ----------
+    using : {"nilearn", "afni", "fsl"}
+        Implementation to use for smoothing:
+
+        * "nilearn" : Use :func:`nilearn.image.smooth_img`
+        * "afni" : Use AFNI's ``3dBlurToFWHM``
+        * "fsl" : Use FSL SUSAN's ``susan``
+
+    on : {"T1w", "T2w", "BOLD"} or list of the options
+        The data type to apply smoothing to.
+    smoothing_params : dict, optional
+        Extra parameters for smoothing as a dictionary (default None).
+        If ``using="nilearn"``, then the valid keys are:
+
+        * ``fmhw`` : scalar, ``numpy.ndarray``, tuple or list of scalar, \
+                     "fast" or None
+            Smoothing strength, as a full-width at half maximum, in
+            millimeters:
+
+            - If nonzero scalar, width is identical in all 3 directions.
+            - If ``numpy.ndarray``, tuple, or list, it must have 3 elements,
+              giving the FWHM along each axis. If any of the elements is 0 or
+              None, smoothing is not performed along that axis.
+            - If ``"fast"``, a fast smoothing will be performed with a filter
+              ``[0.2, 1, 0.2]`` in each direction and a normalisation to
+              preserve the local average value.
+            - If None, no filtering is performed (useful when just removal of
+              non-finite values is needed).
+
+        else if ``using="afni"``, then the valid keys are:
+
+        * ``fwhm`` : int or float
+            Smooth until the value. AFNI estimates the smoothing and then
+            applies smoothing to reach ``fwhm``.
+
+        else if ``using="fsl"``, then the valid keys are:
+
+        * ``brightness_threshold`` : float
+            Threshold to discriminate between noise and the underlying image.
+            The value should be set greater than the noise level and less than
+            the contrast of the underlying image.
+        * ``fwhm`` : float
+            Spatial extent of smoothing.
+
+    """
+
+    _CONDITIONAL_DEPENDENCIES: ClassVar[List[Dict[str, Union[str, Type]]]] = [
+        {
+            "using": "nilearn",
+            "depends_on": NilearnSmoothing,
+        },
+        {
+            "using": "afni",
+            "depends_on": AFNISmoothing,
+        },
+        {
+            "using": "fsl",
+            "depends_on": FSLSmoothing,
+        },
+    ]
+
+    def __init__(
+        self,
+        using: str,
+        on: Union[List[str], str],
+        smoothing_params: Optional[Dict] = None,
+    ) -> None:
+        """Initialize the class."""
+        # Validate `using` parameter
+        valid_using = [dep["using"] for dep in self._CONDITIONAL_DEPENDENCIES]
+        if using not in valid_using:
+            raise_error(
+                f"Invalid value for `using`, should be one of: {valid_using}"
+            )
+        self.using = using
+        self.smoothing_params = (
+            smoothing_params if smoothing_params is not None else {}
+        )
+        super().__init__(on=on)
+
+    def get_valid_inputs(self) -> List[str]:
+        """Get valid data types for input.
+
+        Returns
+        -------
+        list of str
+            The list of data types that can be used as input for this
+            preprocessor.
+
+        """
+        return ["T1w", "T2w", "BOLD"]
+
+    def get_output_type(self, input_type: str) -> str:
+        """Get output type.
+
+        Parameters
+        ----------
+        input_type : str
+            The data type input to the preprocessor.
+
+        Returns
+        -------
+        str
+            The data type output by the preprocessor.
+
+        """
+        # Does not add any new keys
+        return input_type
+
+    def preprocess(
+        self,
+        input: Dict[str, Any],
+        extra_input: Optional[Dict[str, Any]] = None,
+    ) -> Tuple[Dict[str, Any], Optional[Dict[str, Dict[str, Any]]]]:
+        """Preprocess.
+
+        Parameters
+        ----------
+        input : dict
+            The input from the Junifer Data object.
+        extra_input : dict, optional
+            The other fields in the Junifer Data object.
+
+        Returns
+        -------
+        dict
+            The computed result as dictionary.
+        None
+            Extra "helper" data types as dictionary to add to the Junifer Data
+            object.
+
+        """
+        logger.debug("Smoothing")
+
+        # Conditional preprocessor
+        if self.using == "nilearn":
+            preprocessor = NilearnSmoothing()
+        elif self.using == "afni":
+            preprocessor = AFNISmoothing()
+        elif self.using == "fsl":
+            preprocessor = FSLSmoothing()
+        # Smooth
+        output = preprocessor.preprocess(  # type: ignore
+            data=input["data"],
+            **self.smoothing_params,
+        )
+
+        # Modify target data
+        input["data"] = output
+
+        return input, None
diff --git a/junifer/preprocess/smoothing/tests/test_smoothing.py b/junifer/preprocess/smoothing/tests/test_smoothing.py
new file mode 100644
index 0000000000..6fe66c55b2
--- /dev/null
+++ b/junifer/preprocess/smoothing/tests/test_smoothing.py
@@ -0,0 +1,94 @@
+"""Provide tests for Smoothing."""
+
+# Authors: Synchon Mandal <s.mandal@fz-juelich.de>
+# License: AGPL
+
+
+import pytest
+
+from junifer.datareader import DefaultDataReader
+from junifer.pipeline.utils import _check_afni, _check_fsl
+from junifer.preprocess import Smoothing
+from junifer.testing.datagrabbers import SPMAuditoryTestingDataGrabber
+
+
+@pytest.mark.parametrize(
+    "data_type",
+    ["T1w", "BOLD"],
+)
+def test_Smoothing_nilearn(data_type: str) -> None:
+    """Test Smoothing using nilearn.
+
+    Parameters
+    ----------
+    data_type : str
+        The parametrized data type.
+
+    """
+    with SPMAuditoryTestingDataGrabber() as dg:
+        # Read data
+        element_data = DefaultDataReader().fit_transform(dg["sub001"])
+        # Preprocess data
+        output = Smoothing(
+            using="nilearn",
+            on=data_type,
+            smoothing_params={"fwhm": "fast"},
+        ).fit_transform(element_data)
+
+        assert isinstance(output, dict)
+
+
+@pytest.mark.parametrize(
+    "data_type",
+    ["T1w", "BOLD"],
+)
+@pytest.mark.skipif(
+    _check_afni() is False, reason="requires AFNI to be in PATH"
+)
+def test_Smoothing_afni(data_type: str) -> None:
+    """Test Smoothing using AFNI.
+
+    Parameters
+    ----------
+    data_type : str
+        The parametrized data type.
+
+    """
+    with SPMAuditoryTestingDataGrabber() as dg:
+        # Read data
+        element_data = DefaultDataReader().fit_transform(dg["sub001"])
+        # Preprocess data
+        output = Smoothing(
+            using="afni",
+            on=data_type,
+            smoothing_params={"fwhm": 3},
+        ).fit_transform(element_data)
+
+        assert isinstance(output, dict)
+
+
+@pytest.mark.parametrize(
+    "data_type",
+    ["T1w", "BOLD"],
+)
+@pytest.mark.skipif(_check_fsl() is False, reason="requires FSL to be in PATH")
+def test_Smoothing_fsl(data_type: str) -> None:
+    """Test Smoothing using FSL.
+
+    Parameters
+    ----------
+    data_type : str
+        The parametrized data type.
+
+    """
+    with SPMAuditoryTestingDataGrabber() as dg:
+        # Read data
+        element_data = DefaultDataReader().fit_transform(dg["sub001"])
+        # Preprocess data
+        output = Smoothing(
+            using="fsl",
+            on=data_type,
+            smoothing_params={"brightness_threshold": 10.0, "fwhm": 3.0},
+        ).fit_transform(element_data)
+
+        assert isinstance(output, dict)