diff --git a/packages/pyright-internal/src/analyzer/typeEvaluator.ts b/packages/pyright-internal/src/analyzer/typeEvaluator.ts
index fef8ab2aac4e..b7b01a10c653 100644
--- a/packages/pyright-internal/src/analyzer/typeEvaluator.ts
+++ b/packages/pyright-internal/src/analyzer/typeEvaluator.ts
@@ -26126,6 +26126,20 @@ export function createTypeEvaluator(
                         return boolVal === (intVal === 1);
                     }
 
+                    // `bytes` and `bytearray` are distinct built-in classes
+                    // (neither subclasses the other), but `bytes.__eq__` and
+                    // `bytearray.__eq__` cross-compare by content, so an
+                    // expression like `b"abc" == bytearray(b"abc")` is True
+                    // at runtime. Treat them as comparable so we don't emit
+                    // a spurious `reportUnnecessaryComparison` diagnostic.
+                    // The same applies when one side is a `Literal[bytes]`,
+                    // because the literal is still a `bytes` instance.
+                    const isBytesLike = (t: ClassType) =>
+                        ClassType.isBuiltIn(t, 'bytes') || ClassType.isBuiltIn(t, 'bytearray');
+                    if (isBytesLike(leftType) && isBytesLike(rightType)) {
+                        return true;
+                    }
+
                     return false;
                 }
             }
diff --git a/packages/pyright-internal/src/tests/samples/comparison3.py b/packages/pyright-internal/src/tests/samples/comparison3.py
new file mode 100644
index 000000000000..d0146e2e54e6
--- /dev/null
+++ b/packages/pyright-internal/src/tests/samples/comparison3.py
@@ -0,0 +1,37 @@
+# This sample tests that `bytes` and `bytearray` are treated as
+# comparable types for `==` / `!=`. Although they are distinct built-in
+# classes (neither subclasses the other), their `__eq__` implementations
+# cross-compare by content, so a comparison such as
+# `b"abc" == bytearray(b"abc")` is `True` at runtime. See issue #11433.
+
+
+def func1(b1: bytes, b2: bytearray) -> None:
+    if b1 == b2:
+        pass
+
+    if b1 != b2:
+        pass
+
+    if b2 == b1:
+        pass
+
+    if b2 != b1:
+        pass
+
+
+def func2(b: bytearray) -> None:
+    # Literal[bytes] on the RHS is still a `bytes` instance, so the same
+    # cross-class comparison rule applies.
+    if b == b"\x00\x00\x00\x00":
+        pass
+
+    if b"\x00\x00\x00\x00" == b:
+        pass
+
+
+def func3(b: bytes, s: str) -> None:
+    # bytes vs str remains a real "no overlap" — the special case must
+    # not over-relax. This should still generate an error when
+    # reportUnnecessaryComparison is enabled.
+    if b == s:
+        pass
diff --git a/packages/pyright-internal/src/tests/typeEvaluator6.test.ts b/packages/pyright-internal/src/tests/typeEvaluator6.test.ts
index f633c1a284d0..382e8b3e467f 100644
--- a/packages/pyright-internal/src/tests/typeEvaluator6.test.ts
+++ b/packages/pyright-internal/src/tests/typeEvaluator6.test.ts
@@ -638,6 +638,20 @@ test('Comparison2', () => {
     TestUtils.validateResults(analysisResults2, 18);
 });
 
+test('Comparison3', () => {
+    const configOptions = new ConfigOptions(Uri.empty());
+
+    const analysisResults1 = TestUtils.typeAnalyzeSampleFiles(['comparison3.py'], configOptions);
+    TestUtils.validateResults(analysisResults1, 0);
+
+    // bytes/bytearray comparisons in func1 and func2 must NOT emit the
+    // reportUnnecessaryComparison diagnostic; only the bytes-vs-str case
+    // in func3 should — see issue #11433.
+    configOptions.diagnosticRuleSet.reportUnnecessaryComparison = 'error';
+    const analysisResults2 = TestUtils.typeAnalyzeSampleFiles(['comparison3.py'], configOptions);
+    TestUtils.validateResults(analysisResults2, 1);
+});
+
 test('EmptyContainers1', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['emptyContainers1.py']);
     TestUtils.validateResults(analysisResults, 5);