diff --git a/pyogrio/_compat.py b/pyogrio/_compat.py
index cd67247e..fc3df94d 100644
--- a/pyogrio/_compat.py
+++ b/pyogrio/_compat.py
@@ -8,6 +8,11 @@
 except ImportError:
     pyarrow = None
 
+try:
+    import pyproj
+except ImportError:
+    pyproj = None
+
 try:
     import shapely
 except ImportError:
@@ -27,6 +32,7 @@
 HAS_ARROW_API = __gdal_version__ >= (3, 6, 0)
 HAS_ARROW_WRITE_API = __gdal_version__ >= (3, 8, 0)
 HAS_PYARROW = pyarrow is not None
+HAS_PYPROJ = pyproj is not None
 
 HAS_GEOPANDAS = geopandas is not None
 
diff --git a/pyogrio/tests/conftest.py b/pyogrio/tests/conftest.py
index d562a4d1..85508464 100644
--- a/pyogrio/tests/conftest.py
+++ b/pyogrio/tests/conftest.py
@@ -14,6 +14,7 @@
     HAS_ARROW_WRITE_API,
     HAS_GDAL_GEOS,
     HAS_PYARROW,
+    HAS_PYPROJ,
     HAS_SHAPELY,
 )
 from pyogrio.raw import read, write
@@ -54,6 +55,8 @@ def pytest_report_header(config):
     not HAS_ARROW_API or not HAS_PYARROW, reason="GDAL>=3.6 and pyarrow required"
 )
 
+requires_pyproj = pytest.mark.skipif(not HAS_PYPROJ, reason="pyproj required")
+
 requires_arrow_write_api = pytest.mark.skipif(
     not HAS_ARROW_WRITE_API or not HAS_PYARROW,
     reason="GDAL>=3.8 required for Arrow write API",
diff --git a/pyogrio/tests/test_geopandas_io.py b/pyogrio/tests/test_geopandas_io.py
index 12146c3d..7786afb1 100644
--- a/pyogrio/tests/test_geopandas_io.py
+++ b/pyogrio/tests/test_geopandas_io.py
@@ -20,9 +20,10 @@
     DRIVERS,
     requires_pyarrow_api,
     requires_arrow_write_api,
+    requires_pyproj,
     requires_gdal_geos,
 )
-from pyogrio._compat import PANDAS_GE_15, HAS_ARROW_WRITE_API
+from pyogrio._compat import HAS_PYPROJ, PANDAS_GE_15, HAS_ARROW_WRITE_API
 
 try:
     import pandas as pd
@@ -126,7 +127,8 @@ def test_read_csv_platform_encoding(tmp_path):
 def test_read_dataframe(naturalearth_lowres_all_ext):
     df = read_dataframe(naturalearth_lowres_all_ext)
 
-    assert df.crs == "EPSG:4326"
+    if HAS_PYPROJ:
+        assert df.crs == "EPSG:4326"
     assert len(df) == 177
     assert df.columns.tolist() == [
         "pop_est",
@@ -1071,6 +1073,8 @@ def test_write_empty_geometry(tmp_path):
     # Check that no warning is raised with GeoSeries.notna()
     with warnings.catch_warnings():
         warnings.simplefilter("error", UserWarning)
+        if not HAS_PYPROJ:
+            warnings.filterwarnings("ignore", message="'crs' was not provided.")
         write_dataframe(expected, filename)
     assert filename.exists()
 
@@ -1460,6 +1464,7 @@ def test_write_dataframe_infer_geometry_with_nulls(tmp_path, geoms, ext, use_arr
     "ignore: You will likely lose important projection information"
 )
 @pytest.mark.requires_arrow_write_api
+@requires_pyproj
 def test_custom_crs_io(tmp_path, naturalearth_lowres_all_ext, use_arrow):
     df = read_dataframe(naturalearth_lowres_all_ext)
     # project Belgium to a custom Albers Equal Area projection