diff --git a/keras/src/layers/core/dense.py b/keras/src/layers/core/dense.py
index 8af0120c510..8ccbbfa3c11 100644
--- a/keras/src/layers/core/dense.py
+++ b/keras/src/layers/core/dense.py
@@ -1,4 +1,5 @@
 import math
+import numbers
 
 import ml_dtypes
 
@@ -94,6 +95,16 @@ def __init__(
         lora_alpha=None,
         **kwargs,
     ):
+        if (
+            not isinstance(units, numbers.Integral)
+            or isinstance(units, bool)
+            or units <= 0
+        ):
+            raise ValueError(
+                "Received an invalid value for `units`, expected a positive "
+                f"integer. Received: units={units}"
+            )
+
         super().__init__(activity_regularizer=activity_regularizer, **kwargs)
         self.units = units
         self.activation = activations.get(activation)
diff --git a/keras/src/layers/core/dense_test.py b/keras/src/layers/core/dense_test.py
index 802ca10a1d4..6550367a3fa 100644
--- a/keras/src/layers/core/dense_test.py
+++ b/keras/src/layers/core/dense_test.py
@@ -58,6 +58,17 @@ def test_dense_basics(self):
             supports_masking=True,
         )
 
+    @parameterized.named_parameters(
+        ("zero", 0),
+        ("negative", -3),
+        ("float", 2.5),
+        ("none", None),
+        ("string", "64"),
+    )
+    def test_dense_invalid_units_raises(self, units):
+        with self.assertRaisesRegex(ValueError, "positive integer"):
+            layers.Dense(units)
+
     def test_dense_correctness(self):
         # With bias and activation.
         layer = layers.Dense(units=2, activation="relu")