diff --git a/Lib/test/test_array.py b/Lib/test/test_array.py
index ba9c25c835bc39..943420f4c3f4e8 100755
--- a/Lib/test/test_array.py
+++ b/Lib/test/test_array.py
@@ -1612,6 +1612,13 @@ def test_overflows(self):
         self.assertRaises(OverflowError, array.array, self.typecode, [123456])
         # Overflows also float type:
         self.assertRaises(OverflowError, array.array, self.typecode, [1e300])
+        # A failed append, insert or extend leaves the array unchanged:
+        for x in 123456, 1e300:
+            a = array.array(self.typecode, [1])
+            self.assertRaises(OverflowError, a.append, x)
+            self.assertRaises(OverflowError, a.insert, 0, x)
+            self.assertRaises(OverflowError, a.extend, [x])
+            self.assertEqual(a, array.array(self.typecode, [1]))
 
 class FloatTest(FPTest, unittest.TestCase):
     typecode = 'f'
@@ -1619,6 +1626,12 @@ class FloatTest(FPTest, unittest.TestCase):
 
     def test_overflows(self):
         self.assertRaises(OverflowError, array.array, self.typecode, [1e300])
+        # A failed append, insert or extend leaves the array unchanged:
+        a = array.array(self.typecode, [1])
+        self.assertRaises(OverflowError, a.append, 1e300)
+        self.assertRaises(OverflowError, a.insert, 0, 1e300)
+        self.assertRaises(OverflowError, a.extend, [1e300])
+        self.assertEqual(a, array.array(self.typecode, [1]))
 
 class DoubleTest(FPTest, unittest.TestCase):
     typecode = 'd'
@@ -1649,6 +1662,13 @@ class ComplexFloatTest(CFPTest, unittest.TestCase):
     def test_overflows(self):
         self.assertRaises(OverflowError, array.array, self.typecode, [1e300])
         self.assertRaises(OverflowError, array.array, self.typecode, [1e300j])
+        # A failed append, insert or extend leaves the array unchanged:
+        for x in 1e300, 1e300j:
+            a = array.array(self.typecode, [1])
+            self.assertRaises(OverflowError, a.append, x)
+            self.assertRaises(OverflowError, a.insert, 0, x)
+            self.assertRaises(OverflowError, a.extend, [x])
+            self.assertEqual(a, array.array(self.typecode, [1]))
 
 class ComplexDoubleTest(CFPTest, unittest.TestCase):
     typecode = 'Zd'
diff --git a/Misc/NEWS.d/next/Library/2026-09-28-13-52-36.gh-issue-158345.GNlDCF.rst b/Misc/NEWS.d/next/Library/2026-09-28-13-52-36.gh-issue-158345.GNlDCF.rst
new file mode 100644
index 00000000000000..208b3e8055e54a
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-09-28-13-52-36.gh-issue-158345.GNlDCF.rst
@@ -0,0 +1,3 @@
+Fix :meth:`array.array.append`, :meth:`~array.array.insert` and
+:meth:`~array.array.extend` leaving an extra item in the array when they
+raise :exc:`OverflowError` for the ``'e'``, ``'f'`` or ``'Zf'`` type code.
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index ef492d143d5644..9b5afe09a5e751 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -585,15 +585,18 @@ static int
 e_setitem(arrayobject *ap, Py_ssize_t i, PyObject *v)
 {
     double x;
+    char buf[sizeof(short)];
     if (!PyArg_Parse(v, "d;array item must be float", &x)) {
         return -1;
     }
+    if (PyFloat_Pack2(x, buf, PY_LITTLE_ENDIAN) < 0) {
+        return -1;
+    }
 
     CHECK_ARRAY_BOUNDS(ap, i);
 
     if (i >= 0) {
-        return PyFloat_Pack2(x, ap->ob_item + sizeof(short)*i,
-                             PY_LITTLE_ENDIAN);
+        memcpy(ap->ob_item + sizeof(short)*i, buf, sizeof(buf));
     }
     return 0;
 }
@@ -608,14 +611,17 @@ static int
 f_setitem(arrayobject *ap, Py_ssize_t i, PyObject *v)
 {
     double x;
+    char buf[sizeof(float)];
     if (!PyArg_Parse(v, "d;array item must be float", &x))
         return -1;
+    if (PyFloat_Pack4(x, buf, PY_LITTLE_ENDIAN) < 0) {
+        return -1;
+    }
 
     CHECK_ARRAY_BOUNDS(ap, i);
 
     if (i >= 0) {
-        return PyFloat_Pack4(x, ap->ob_item + sizeof(float)*i,
-                             PY_LITTLE_ENDIAN);
+        memcpy(ap->ob_item + sizeof(float)*i, buf, sizeof(buf));
     }
     return 0;
 }
@@ -653,25 +659,21 @@ static int
 cf_setitem(arrayobject *ap, Py_ssize_t i, PyObject *v)
 {
     Py_complex x;
+    char f[8];
 
     if (!PyArg_Parse(v, "D;array item must be complex", &x)) {
         return -1;
     }
+    if (PyFloat_Pack4(x.real, f, PY_LITTLE_ENDIAN) < 0
+        || PyFloat_Pack4(x.imag, f + sizeof(float), PY_LITTLE_ENDIAN) < 0)
+    {
+        return -1;
+    }
 
     CHECK_ARRAY_BOUNDS(ap, i);
 
     if (i >= 0) {
-        char f[8];
-        int ret = PyFloat_Pack4(x.real, f, PY_LITTLE_ENDIAN);
-
-        if (ret) {
-            return ret;
-        }
-        ret = PyFloat_Pack4(x.imag, f + sizeof(float), PY_LITTLE_ENDIAN);
-        if (!ret) {
-            memcpy(ap->ob_item + i*sizeof(f), &f, sizeof(f));
-        }
-        return ret;
+        memcpy(ap->ob_item + i*sizeof(f), &f, sizeof(f));
     }
     return 0;
 }