diff --git a/packages/google-api-core/google/api_core/path_template.py b/packages/google-api-core/google/api_core/path_template.py
index 069112ae6e6b..128a923ae76b 100644
--- a/packages/google-api-core/google/api_core/path_template.py
+++ b/packages/google-api-core/google/api_core/path_template.py
@@ -123,7 +123,7 @@ def _expand_variable_match(positional_vars, named_vars, match):
         try:
             val = str(named_vars[name])
             _extract_and_validate_wildcards(val, template, name)
-            return urllib.parse.quote(val, safe="/")
+            return urllib.parse.quote(val, safe="/():")
         except KeyError:
             raise ValueError(
                 "Named variable '{}' not specified and needed by template "
@@ -133,7 +133,7 @@ def _expand_variable_match(positional_vars, named_vars, match):
         try:
             val = str(positional_vars.pop(0))
             _extract_and_validate_wildcards(val, positional, "positional variable")
-            return urllib.parse.quote(val, safe="/")
+            return urllib.parse.quote(val, safe="/():")
         except IndexError:
             raise ValueError(
                 "Positional variable not specified and needed by template "
diff --git a/packages/google-api-core/tests/unit/test_path_template.py b/packages/google-api-core/tests/unit/test_path_template.py
index e8dead5edc6d..05edaa117205 100644
--- a/packages/google-api-core/tests/unit/test_path_template.py
+++ b/packages/google-api-core/tests/unit/test_path_template.py
@@ -64,6 +64,39 @@
             {"name": "parent/child/object"},
             "/v1/a/parent/child/object",
         ],
+        # See https://github.com/googleapis/google-cloud-python/issues/18213
+        # Test parentheses in resource paths
+        [
+            "projects/{project}/databases/{database}",
+            [],
+            {"project": "my-project", "database": "(default)"},
+            "projects/my-project/databases/(default)",
+        ],
+        [
+            "projects/{project}/databases/{database}/**",
+            ["documents/user_1"],
+            {"project": "my-project", "database": "(default)"},
+            "projects/my-project/databases/(default)/documents/user_1",
+        ],
+        [
+            "/v1/{name=projects/*/databases/*}",
+            [],
+            {"name": "projects/my-project/databases/(default)"},
+            "/v1/projects/my-project/databases/(default)",
+        ],
+        # Test colon in resource paths
+        [
+            "/v1/{name}",
+            [],
+            {"name": "my-instance:cluster-1"},
+            "/v1/my-instance:cluster-1",
+        ],
+        [
+            "/v1/{name=**}",
+            [],
+            {"name": "instances/my-instance:cluster-1"},
+            "/v1/instances/my-instance:cluster-1",
+        ],
         # Encoding / Metacharacters in positional and named params
         ["/v1/*", ["..?$httpMethod=DELETE#"], {}, "/v1/..%3F%24httpMethod%3DDELETE%23"],
         ["/v1/**", ["path/sub/with/?and#"], {}, "/v1/path/sub/with/%3Fand%23"],