diff --git a/src/agents/models/_retry_runtime.py b/src/agents/models/_retry_runtime.py
index 718931f403..5d6f427ad2 100644
--- a/src/agents/models/_retry_runtime.py
+++ b/src/agents/models/_retry_runtime.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import math
 import time
 from collections.abc import Iterator, Mapping
 from contextlib import contextmanager
@@ -64,7 +65,7 @@ def parse_retry_after_ms(value: str | None) -> float | None:
         parsed = float(value) / 1000.0
     except ValueError:
         return None
-    return parsed if parsed >= 0 else None
+    return parsed if math.isfinite(parsed) and parsed >= 0 else None
 
 
 def parse_retry_after_value(value: str | None) -> float | None:
@@ -76,7 +77,7 @@ def parse_retry_after_value(value: str | None) -> float | None:
     except ValueError:
         parsed = None
     if parsed is not None:
-        return parsed if parsed >= 0 else None
+        return parsed if math.isfinite(parsed) and parsed >= 0 else None
 
     try:
         retry_datetime = parsedate_to_datetime(value)
diff --git a/tests/models/test_retry_after_nonfinite.py b/tests/models/test_retry_after_nonfinite.py
new file mode 100644
index 0000000000..c82fb6e6cf
--- /dev/null
+++ b/tests/models/test_retry_after_nonfinite.py
@@ -0,0 +1,18 @@
+import pytest
+
+from agents.models._retry_runtime import parse_retry_after_ms, parse_retry_after_value
+
+
+@pytest.mark.parametrize("value", ["Infinity", "+Infinity", "-Infinity", "NaN"])
+def test_retry_after_ms_rejects_non_finite_values(value: str) -> None:
+    assert parse_retry_after_ms(value) is None
+
+
+@pytest.mark.parametrize("value", ["Infinity", "+Infinity", "-Infinity", "NaN"])
+def test_retry_after_rejects_non_finite_numeric_values(value: str) -> None:
+    assert parse_retry_after_value(value) is None
+
+
+def test_retry_after_parsers_keep_finite_values() -> None:
+    assert parse_retry_after_ms("1500") == 1.5
+    assert parse_retry_after_value("2.5") == 2.5