diff --git a/src/aind_data_schema/core/procedures.py b/src/aind_data_schema/core/procedures.py
index cb5754b54..58b7ea3e4 100644
--- a/src/aind_data_schema/core/procedures.py
+++ b/src/aind_data_schema/core/procedures.py
@@ -79,7 +79,13 @@ def validate_subject_specimen_ids(self):
         # Return if no specimen procedures
         if self.specimen_procedures:
             subject_id = self.subject_id
-            specimen_ids = [spec_proc.specimen_id for spec_proc in self.specimen_procedures]
+            specimen_id_vars = [spec_proc.specimen_id for spec_proc in self.specimen_procedures]
+            specimen_ids = []
+            for spec_id_var in specimen_id_vars:
+                if isinstance(spec_id_var, str):
+                    specimen_ids.append(spec_id_var)
+                else:
+                    specimen_ids.extend(spec_id_var)
 
             if any(not subject_specimen_id_compatibility(subject_id, spec_id) for spec_id in specimen_ids):
                 raise ValueError("specimen_id must be an extension of the subject_id.")
diff --git a/tests/test_procedures.py b/tests/test_procedures.py
index c384893e6..d808d6c0d 100644
--- a/tests/test_procedures.py
+++ b/tests/test_procedures.py
@@ -516,6 +516,25 @@ def test_validate_subject_specimen_ids(self):
         expected_exception = "specimen_id must be an extension of the subject_id."
         self.assertIn(expected_exception, str(e.exception))
 
+    def test_validate_subject_specimen_id_list_valid(self):
+        """Test that specimen_id accepts a list of strings when all contain subject_id"""
+
+        valid_procedure = Procedures(
+                subject_id="12345",
+                specimen_procedures=[
+                    SpecimenProcedure(
+                        specimen_id=["12345_001", "12345_002"],
+                        procedure_type="Other",
+                        start_date=date.fromisoformat("2020-10-10"),
+                        end_date=date.fromisoformat("2020-10-11"),
+                        experimenters=["Mam Moth"],
+                        protocol_id=["10"],
+                        notes="some notes",
+                    )
+                ],
+            )
+        self.assertIsNotNone(valid_procedure)
+
     def test_craniotomy_position_validation(self):
         """Test validation for craniotomy position"""