diff --git a/packages/gapic-generator/gapic/schema/api.py b/packages/gapic-generator/gapic/schema/api.py
index 4ee478a64398..bdb8031d147b 100644
--- a/packages/gapic-generator/gapic/schema/api.py
+++ b/packages/gapic-generator/gapic/schema/api.py
@@ -169,10 +169,16 @@ def resource_messages(self) -> Mapping[str, wrappers.MessageType]:
             for msg in self.messages.values()
             if msg.options.Extensions[resource_pb2.resource].type
         )
+
+        # Convert the set to a sorted tuple using the resource path or message name.
+        # This is needed to prevent non-deterministic code generation.
         return collections.OrderedDict(
-            itertools.chain(
-                file_resource_messages,
-                resource_messages,
+            sorted(
+                itertools.chain(
+                    file_resource_messages,
+                    resource_messages,
+                ),
+                key=lambda item: item[0]
             )
         )
 
diff --git a/packages/gapic-generator/gapic/schema/wrappers.py b/packages/gapic-generator/gapic/schema/wrappers.py
index f654d0a82d18..ce74043798e2 100644
--- a/packages/gapic-generator/gapic/schema/wrappers.py
+++ b/packages/gapic-generator/gapic/schema/wrappers.py
@@ -2278,7 +2278,7 @@ def names(self) -> FrozenSet[str]:
         return frozenset(answer)
 
     @utils.cached_property
-    def resource_messages(self) -> FrozenSet[MessageType]:
+    def resource_messages(self) -> Sequence['MessageType']:
         """Returns all the resource message types used in all
         request and response fields in the service."""
 
@@ -2301,7 +2301,7 @@ def gen_indirect_resources_used(message):
                 if resource:
                     yield resource
 
-        return frozenset(
+        unique_messages = frozenset(
             msg
             for method in self.methods.values()
             for msg in chain(
@@ -2316,6 +2316,15 @@ def gen_indirect_resources_used(message):
             )
         )
 
+        # Convert the set to a sorted tuple using the resource path or message name.
+        # This is needed to prevent non-deterministic code generation.
+        sorted_messages = sorted(
+            unique_messages,
+            key=lambda m: m.resource_type_full_path or m.name
+        )
+
+        return tuple(sorted_messages)
+
     @utils.cached_property
     def resource_messages_dict(self) -> Dict[str, MessageType]:
         """Returns a dict from resource reference to
diff --git a/packages/gapic-generator/tests/unit/schema/test_api.py b/packages/gapic-generator/tests/unit/schema/test_api.py
index 9d2dab2ec6a1..9d94e8251523 100644
--- a/packages/gapic-generator/tests/unit/schema/test_api.py
+++ b/packages/gapic-generator/tests/unit/schema/test_api.py
@@ -1740,17 +1740,17 @@ def test_file_level_resources():
     expected = collections.OrderedDict(
         (
             (
-                "nomenclature.linnaen.com/Species",
+                "nomenclature.linnaen.com/Phylum",
                 wrappers.CommonResource(
-                    type_name="nomenclature.linnaen.com/Species",
-                    pattern="families/{family}/genera/{genus}/species/{species}",
+                    type_name="nomenclature.linnaen.com/Phylum",
+                    pattern="kingdoms/{kingdom}/phyla/{phylum}",
                 ).message_type,
             ),
             (
-                "nomenclature.linnaen.com/Phylum",
+                "nomenclature.linnaen.com/Species",
                 wrappers.CommonResource(
-                    type_name="nomenclature.linnaen.com/Phylum",
-                    pattern="kingdoms/{kingdom}/phyla/{phylum}",
+                    type_name="nomenclature.linnaen.com/Species",
+                    pattern="families/{family}/genera/{genus}/species/{species}",
                 ).message_type,
             ),
         )
@@ -1767,7 +1767,7 @@ def test_file_level_resources():
     # The service doesn't own any method that owns a message that references
     # Phylum, so the service doesn't count it among its resource messages.
     expected.pop("nomenclature.linnaen.com/Phylum")
-    expected = frozenset(expected.values())
+    expected = tuple(expected.values())
     actual = service.resource_messages
 
     assert actual == expected
@@ -1822,7 +1822,7 @@ def test_resources_referenced_but_not_typed(reference_attr="type"):
         name_resource_opts.child_type = species_resource_opts.type
 
     api_schema = api.API.build([fdp], package="nomenclature.linneaen.v1")
-    expected = {api_schema.messages["nomenclature.linneaen.v1.Species"]}
+    expected = (api_schema.messages["nomenclature.linneaen.v1.Species"],)
     actual = api_schema.services[
         "nomenclature.linneaen.v1.SpeciesService"
     ].resource_messages
diff --git a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
index eb54577b2e51..04f7ac7308ea 100644
--- a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
+++ b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
@@ -267,12 +267,12 @@ def test_resource_messages():
         ),
     )
 
-    expected = {
-        squid_resource,
+    expected = (
         clam_resource,
-        whelk_resource,
         squamosa_message,
-    }
+        squid_resource,
+        whelk_resource,
+    )
     actual = service.resource_messages
     assert expected == actual
 
@@ -557,7 +557,7 @@ def test_resource_response():
         ),
     )
 
-    expected = {squid_resource, clam_resource}
+    expected = (clam_resource, squid_resource)
     actual = mollusc_service.resource_messages
     assert expected == actual