diff --git a/changelog/7815.doc.rst b/changelog/7815.doc.rst
new file mode 100644
index 00000000000..d799bb42500
--- /dev/null
+++ b/changelog/7815.doc.rst
@@ -0,0 +1 @@
+Improve deprecation warning message for ``pytest._fillfuncargs()``.
diff --git a/src/_pytest/deprecated.py b/src/_pytest/deprecated.py
index ecdb60d37f5..fd00fe2d6d5 100644
--- a/src/_pytest/deprecated.py
+++ b/src/_pytest/deprecated.py
@@ -20,9 +20,10 @@
 }
 
 
-FILLFUNCARGS = PytestDeprecationWarning(
-    "The `_fillfuncargs` function is deprecated, use "
-    "function._request._fillfixtures() instead if you cannot avoid reaching into internals."
+FILLFUNCARGS = UnformattedWarning(
+    PytestDeprecationWarning,
+    "{name} is deprecated, use "
+    "function._request._fillfixtures() instead if you cannot avoid reaching into internals.",
 )
 
 PYTEST_COLLECT_MODULE = UnformattedWarning(
diff --git a/src/_pytest/fixtures.py b/src/_pytest/fixtures.py
index f526f484b29..a299b2dba50 100644
--- a/src/_pytest/fixtures.py
+++ b/src/_pytest/fixtures.py
@@ -339,9 +339,22 @@ def reorder_items_atscope(
     return items_done
 
 
+def _fillfuncargs(function: "Function") -> None:
+    """Fill missing fixtures for a test function, old public API (deprecated)."""
+    warnings.warn(FILLFUNCARGS.format(name="pytest._fillfuncargs()"), stacklevel=2)
+    _fill_fixtures_impl(function)
+
+
 def fillfixtures(function: "Function") -> None:
-    """Fill missing funcargs for a test function."""
-    warnings.warn(FILLFUNCARGS, stacklevel=2)
+    """Fill missing fixtures for a test function (deprecated)."""
+    warnings.warn(
+        FILLFUNCARGS.format(name="_pytest.fixtures.fillfixtures()"), stacklevel=2
+    )
+    _fill_fixtures_impl(function)
+
+
+def _fill_fixtures_impl(function: "Function") -> None:
+    """Internal implementation to fill fixtures on the given function object."""
     try:
         request = function._request
     except AttributeError:
diff --git a/src/pytest/__init__.py b/src/pytest/__init__.py
index c4c28191877..a9c1ee0282b 100644
--- a/src/pytest/__init__.py
+++ b/src/pytest/__init__.py
@@ -11,7 +11,7 @@
 from _pytest.config import main
 from _pytest.config import UsageError
 from _pytest.debugging import pytestPDB as __pytestPDB
-from _pytest.fixtures import fillfixtures as _fillfuncargs
+from _pytest.fixtures import _fillfuncargs
 from _pytest.fixtures import fixture
 from _pytest.fixtures import FixtureLookupError
 from _pytest.fixtures import yield_fixture
diff --git a/testing/deprecated_test.py b/testing/deprecated_test.py
index eb5d527f52b..5fe9ad7305f 100644
--- a/testing/deprecated_test.py
+++ b/testing/deprecated_test.py
@@ -1,3 +1,4 @@
+import re
 import warnings
 from unittest import mock
 
@@ -26,11 +27,27 @@ def test_external_plugins_integrated(testdir, plugin):
 def test_fillfuncargs_is_deprecated() -> None:
     with pytest.warns(
         pytest.PytestDeprecationWarning,
-        match="The `_fillfuncargs` function is deprecated",
+        match=re.escape(
+            "pytest._fillfuncargs() is deprecated, use "
+            "function._request._fillfixtures() instead if you cannot avoid reaching into internals."
+        ),
     ):
         pytest._fillfuncargs(mock.Mock())
 
 
+def test_fillfixtures_is_deprecated() -> None:
+    import _pytest.fixtures
+
+    with pytest.warns(
+        pytest.PytestDeprecationWarning,
+        match=re.escape(
+            "_pytest.fixtures.fillfixtures() is deprecated, use "
+            "function._request._fillfixtures() instead if you cannot avoid reaching into internals."
+        ),
+    ):
+        _pytest.fixtures.fillfixtures(mock.Mock())
+
+
 def test_minus_k_dash_is_deprecated(testdir) -> None:
     threepass = testdir.makepyfile(
         test_threepass="""
diff --git a/testing/python/fixtures.py b/testing/python/fixtures.py
index 9ae5a91db43..67b7ad60116 100644
--- a/testing/python/fixtures.py
+++ b/testing/python/fixtures.py
@@ -87,7 +87,7 @@ class T:
 class TestFillFixtures:
     def test_fillfuncargs_exposed(self):
         # used by oejskit, kept for compatibility
-        assert pytest._fillfuncargs == fixtures.fillfixtures
+        assert pytest._fillfuncargs == fixtures._fillfuncargs
 
     def test_funcarg_lookupfails(self, testdir):
         testdir.copy_example()