diff --git a/changelog/9113.feature.rst b/changelog/9113.feature.rst
new file mode 100644
index 000000000..f16e6ea63
--- /dev/null
+++ b/changelog/9113.feature.rst
@@ -0,0 +1,2 @@
+:class:`RunResult <_pytest.pytester.RunResult>` method :meth:`assert_outcomes <_pytest.pytester.RunResult.assert_outcomes>` now accepts a
+``deselected`` argument to assert the total number of deselected tests.
diff --git a/src/_pytest/pytester.py b/src/_pytest/pytester.py
index c8258d4b6..9933f7946 100644
--- a/src/_pytest/pytester.py
+++ b/src/_pytest/pytester.py
@@ -589,6 +589,7 @@ class RunResult:
         xpassed: int = 0,
         xfailed: int = 0,
         warnings: int = 0,
+        deselected: int = 0,
     ) -> None:
         """Assert that the specified outcomes appear with the respective
         numbers (0 means it didn't occur) in the text output from a test run."""
@@ -605,6 +606,7 @@ class RunResult:
             xpassed=xpassed,
             xfailed=xfailed,
             warnings=warnings,
+            deselected=deselected,
         )
 
 
diff --git a/src/_pytest/pytester_assertions.py b/src/_pytest/pytester_assertions.py
index 45aa41c5a..6a5aabece 100644
--- a/src/_pytest/pytester_assertions.py
+++ b/src/_pytest/pytester_assertions.py
@@ -43,6 +43,7 @@ def assert_outcomes(
     xpassed: int = 0,
     xfailed: int = 0,
     warnings: int = 0,
+    deselected: int = 0,
 ) -> None:
     """Assert that the specified outcomes appear with the respective
     numbers (0 means it didn't occur) in the text output from a test run."""
@@ -56,6 +57,7 @@ def assert_outcomes(
         "xpassed": outcomes.get("xpassed", 0),
         "xfailed": outcomes.get("xfailed", 0),
         "warnings": outcomes.get("warnings", 0),
+        "deselected": outcomes.get("deselected", 0),
     }
     expected = {
         "passed": passed,
@@ -65,5 +67,6 @@ def assert_outcomes(
         "xpassed": xpassed,
         "xfailed": xfailed,
         "warnings": warnings,
+        "deselected": deselected,
     }
     assert obtained == expected
diff --git a/testing/test_pytester.py b/testing/test_pytester.py
index b0a94223c..d9c97c896 100644
--- a/testing/test_pytester.py
+++ b/testing/test_pytester.py
@@ -861,3 +861,17 @@ def test_pytester_assert_outcomes_warnings(pytester: Pytester) -> None:
     )
     result = pytester.runpytest()
     result.assert_outcomes(passed=1, warnings=1)
+
+
+def test_pytester_outcomes_deselected(pytester: Pytester) -> None:
+    pytester.makepyfile(
+        """
+        def test_one():
+            pass
+
+        def test_two():
+            pass
+        """
+    )
+    result = pytester.runpytest("-k", "test_one")
+    result.assert_outcomes(passed=1, deselected=1)