diff --git a/.github/workflows/validation.yaml b/.github/workflows/validation.yaml
index 3c06160..ba1bf81 100644
--- a/.github/workflows/validation.yaml
+++ b/.github/workflows/validation.yaml
@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
     steps:
     - uses: actions/checkout@v6
     - uses: actions/setup-python@v6
diff --git a/pyproject.toml b/pyproject.toml
index fada008..0db2324 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,6 +24,7 @@ classifiers = [
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: 3.15",
     "Programming Language :: Python :: Implementation :: CPython",
     "Topic :: Software Development :: Testing",
 ]
diff --git a/tests/test_pytest_mypy.py b/tests/test_pytest_mypy.py
index 820704b..803bbe6 100644
--- a/tests/test_pytest_mypy.py
+++ b/tests/test_pytest_mypy.py
@@ -83,6 +83,10 @@ def test_mypy_encoding_warnings(testdir, monkeypatch):
         # Use typing.TypedDict or typing_extensions.TypedDict instead.
         # https://github.com/python/mypy/pull/15494
         expected_warnings += 1
+    elif MYPY_VERSION < Version("2.3") and PYTHON_VERSION >= Version("3.15"):
+        # Mypy 2.3 added compiled .so modules for mypy.modulefinder and mypy.build.
+        # https://github.com/python/mypy/pull/21255
+        expected_warnings += 1
     elif MYPY_VERSION >= Version("2.4"):
         # https://github.com/python/mypy/pull/21823
         expected_warnings -= 1
diff --git a/tox.ini b/tox.ini
index 6869ecb..962681b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,6 +8,7 @@ envlist =
     py312-pytest{7.0, 7.x, 8.0, 8.x, 9.0, 9.x}-mypy{1.0, 1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
     py313-pytest{7.0, 7.x, 8.0, 8.x, 9.0, 9.x}-mypy{1.0, 1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
     py314-pytest{     7.x, 8.0, 8.x, 9.0, 9.x}-mypy{     1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
+    py315-pytest{     7.x, 8.0, 8.x, 9.0, 9.x}-mypy{     1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
     static
     publish
 
@@ -18,6 +19,7 @@ python =
     3.12: py312-pytest{7.0, 7.x, 8.0, 8.x, 9.0, 9.x}-mypy{1.0, 1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
     3.13: py313-pytest{7.0, 7.x, 8.0, 8.x, 9.0, 9.x}-mypy{1.0, 1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
     3.14: py314-pytest{     7.x, 8.0, 8.x, 9.0, 9.x}-mypy{     1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
+    3.15: py315-pytest{     7.x, 8.0, 8.x, 9.0, 9.x}-mypy{     1.x, 2.0, 2.x}-xdist{2.0, 2.x, 3.0, 3.x}
 
 [testenv]
 constrain_package_deps = true