diff --git a/changelog/14050.bugfix.rst b/changelog/14050.bugfix.rst
new file mode 100644
index 00000000000..451b248576f
--- /dev/null
+++ b/changelog/14050.bugfix.rst
@@ -0,0 +1 @@
+Display dictionary differences in assertion failures using the original key insertion order instead of sorted order.
diff --git a/src/_pytest/_io/pprint.py b/src/_pytest/_io/pprint.py
index 28f06909206..ec41b449ddf 100644
--- a/src/_pytest/_io/pprint.py
+++ b/src/_pytest/_io/pprint.py
@@ -162,7 +162,7 @@ def _pprint_dict(
     ) -> None:
         write = stream.write
         write("{")
-        items = sorted(object.items(), key=_safe_tuple)
+        items = object.items()
         self._format_dict_items(items, stream, indent, allowance, context, level)
         write("}")
 
@@ -608,7 +608,7 @@ def _safe_repr(
             components: list[str] = []
             append = components.append
             level += 1
-            for k, v in sorted(object.items(), key=_safe_tuple):
+            for k, v in object.items():
                 krepr = self._safe_repr(k, context, maxlevels, level)
                 vrepr = self._safe_repr(v, context, maxlevels, level)
                 append(f"{krepr}: {vrepr}")
diff --git a/src/_pytest/_io/saferepr.py b/src/_pytest/_io/saferepr.py
index cee70e332f9..3f5c956d9cf 100644
--- a/src/_pytest/_io/saferepr.py
+++ b/src/_pytest/_io/saferepr.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from itertools import islice
 import pprint
 import reprlib
 
@@ -77,8 +78,32 @@ def repr_instance(self, x: object, level: int) -> str:
             s = _format_repr_exception(exc, x)
         if self.maxsize is not None:
             s = _ellipsize(s, self.maxsize)
+
         return s
 
+    def repr_dict(self, x: dict[object, object], level: int) -> str:
+        """Represent a dict while preserving its insertion order.
+
+        Differs from ``reprlib.Repr.repr_dict`` by iterating directly over ``x``
+        rather than using the stdlib's sorting helper.
+        """
+        fillvalue = "..."
+        n = len(x)
+        if n == 0:
+            return "{}"
+        if level <= 0:
+            return "{" + fillvalue + "}"
+        newlevel = level - 1
+        repr1 = self.repr1
+        pieces = []
+        for key in islice(x, self.maxdict):
+            keyrepr = repr1(key, newlevel)
+            valrepr = repr1(x[key], newlevel)
+            pieces.append(f"{keyrepr}: {valrepr}")
+        if n > self.maxdict:
+            pieces.append(fillvalue)
+        return "{" + ", ".join(pieces) + "}"
+
 
 def safeformat(obj: object) -> str:
     """Return a pretty printed string for the given object.
diff --git a/src/_pytest/pytester_assertions.py b/src/_pytest/pytester_assertions.py
index 915cc8a10ff..b8d8a195241 100644
--- a/src/_pytest/pytester_assertions.py
+++ b/src/_pytest/pytester_assertions.py
@@ -26,11 +26,11 @@ def assertoutcome(
 
     realpassed, realskipped, realfailed = outcomes
     obtained = {
+        "failed": len(realfailed),
         "passed": len(realpassed),
         "skipped": len(realskipped),
-        "failed": len(realfailed),
     }
-    expected = {"passed": passed, "skipped": skipped, "failed": failed}
+    expected = {"failed": failed, "passed": passed, "skipped": skipped}
     assert obtained == expected, outcomes
 
 
diff --git a/testing/io/test_saferepr.py b/testing/io/test_saferepr.py
index 075d40cdf44..2e3dd55b81f 100644
--- a/testing/io/test_saferepr.py
+++ b/testing/io/test_saferepr.py
@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 from _pytest._io.saferepr import DEFAULT_REPR_MAX_SIZE
+from _pytest._io.saferepr import SafeRepr
 from _pytest._io.saferepr import saferepr
 from _pytest._io.saferepr import saferepr_unlimited
 import pytest
@@ -192,3 +193,39 @@ def __repr__(self):
     assert saferepr_unlimited(A()).startswith(
         "<[ValueError(42) raised in repr()] A object at 0x"
     )
+
+
+def test_saferepr_dict_preserves_insertion_order() -> None:
+    d = {
+        "b": 2,
+        "a": 1,
+        "d": 4,
+        "e": 5,
+        "c": 3,
+    }
+    s = SafeRepr(maxsize=None)
+    s.maxdict = 10
+    assert s.repr(d) == "{'b': 2, 'a': 1, 'd': 4, 'e': 5, 'c': 3}"
+
+
+def test_saferepr_dict_truncation_preserves_insertion_order() -> None:
+    d = {
+        "b": 2,
+        "a": 1,
+        "d": 4,
+        "e": 5,
+        "c": 3,
+    }
+    s = SafeRepr(maxsize=None)
+    s.maxdict = 1
+    assert s.repr(d) == "{'b': 2, ...}"
+
+
+def test_saferepr_dict_fillvalue_when_level_is_zero() -> None:
+    s = SafeRepr(maxsize=None)
+    assert s.repr_dict({"a": 1}, level=0) == "{...}"
+
+
+def test_saferepr_dict_empty() -> None:
+    s = SafeRepr(maxsize=None)
+    assert s.repr_dict({}, level=1) == "{}"
diff --git a/testing/test_assertion.py b/testing/test_assertion.py
index 9c9881cf8ed..d68fd0b1fba 100644
--- a/testing/test_assertion.py
+++ b/testing/test_assertion.py
@@ -2209,3 +2209,34 @@ def test_vvv():
         ]
     )
     result.stdout.no_fnmatch_line(expected_non_vvv_arg_line)
+
+
+def test_dict_extra_items_preserve_insertion_order(pytester: Pytester) -> None:
+    """Assertion output of dict diff shows keys in insertion order (#13503)."""
+    pytester.makepyfile(
+        test_order="""
+        def test_order():
+            a = {
+                "b": 2,
+                "a": 1,
+                "d": 4,
+                "e": 5,
+                "c": 3,
+            }
+            assert a == {}
+        """
+    )
+
+    result = pytester.runpytest("-vv")
+    result.stdout.fnmatch_lines(
+        [
+            "*Left contains 5 more items:*",
+            "*Full diff:",
+            "* + *'b': 2,",
+            "* + *'a': 1,",
+            "* + *'d': 4,",
+            "* + *'e': 5,",
+            "* + *'c': 3,",
+            "test_order.py:*: AssertionError",
+        ]
+    )