diff --git a/cid/set.py b/cid/set.py
index ab5d4e1..3f28eb8 100644
--- a/cid/set.py
+++ b/cid/set.py
@@ -1,7 +1,7 @@
 """CID Set operations for managing collections of unique CIDs."""
 
 from collections.abc import Callable
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any
 
 if TYPE_CHECKING:
     from .cid import CIDv0, CIDv1
@@ -77,15 +77,22 @@ def visit(self, cid: "CIDv0 | CIDv1") -> bool:
             return True
         return False
 
-    def for_each(self, func: Callable[["CIDv0 | CIDv1"], None]) -> None:
+    def for_each(self, func: Callable[["CIDv0 | CIDv1"], "Any"]) -> "Exception | None":
         """
-        Call function for each CID in set.
+        Call function for each CID in set. Stop and return error if func raises or returns an error.
 
         :param func: Function to call for each CID
         :type func: callable
+        :return: Exception if an error occurred, None otherwise
         """
         for cid in self._set:
-            func(cid)
+            try:
+                result = func(cid)
+                if result is not None and isinstance(result, Exception):
+                    return result
+            except Exception as e:
+                return e
+        return None
 
     def __iter__(self):
         """Make set iterable."""
diff --git a/newsfragments/69.bugfix.rst b/newsfragments/69.bugfix.rst
new file mode 100644
index 0000000..9e6e953
--- /dev/null
+++ b/newsfragments/69.bugfix.rst
@@ -0,0 +1 @@
+Update `CIDSet.for_each()` to stop iteration and return the error if the callback function raises an exception or returns an exception.
diff --git a/tests/test_new_features.py b/tests/test_new_features.py
index 04c766e..afb570d 100644
--- a/tests/test_new_features.py
+++ b/tests/test_new_features.py
@@ -262,6 +262,26 @@ def collect(cid):
         assert cidv0 in collected
         assert cidv1 in collected
 
+    def test_cid_set_for_each_error_propagation(self, cidv0, cidv1):
+        """CIDSet.for_each: stops and propagates error"""
+        cid_set = CIDSet()
+        cid_set.add(cidv0)
+        cid_set.add(cidv1)
+
+        def failing_func(cid):
+            raise ValueError("test error")
+
+        result = cid_set.for_each(failing_func)
+        assert isinstance(result, ValueError)
+        assert str(result) == "test error"
+
+        def returning_func(cid):
+            return TypeError("return error")
+
+        result2 = cid_set.for_each(returning_func)
+        assert isinstance(result2, TypeError)
+        assert str(result2) == "return error"
+
     def test_cid_set_contains(self, cidv0):
         """CIDSet.__contains__: supports 'in' operator"""
         cid_set = CIDSet()