diff --git a/src/registrar/admin.py b/src/registrar/admin.py
index d3530101d..2151d6f3c 100644
--- a/src/registrar/admin.py
+++ b/src/registrar/admin.py
@@ -3193,9 +3193,6 @@ class PortfolioAdmin(ListHeaderAdmin):
             return self.add_fieldsets
         return super().get_fieldsets(request, obj)
 
-    # TODO - I think the solution to this may just be to set this as editable.
-    # Then in the underlying page override, we need a fake readonly display that
-    # is toggled on or off.
     def get_readonly_fields(self, request, obj=None):
         """Set the read-only state on form elements.
         We have 2 conditions that determine which fields are read-only:
@@ -3241,7 +3238,6 @@ class PortfolioAdmin(ListHeaderAdmin):
         return super().change_view(request, object_id, form_url, extra_context)
 
     def save_model(self, request, obj: Portfolio, form, change):
-
         if hasattr(obj, "creator") is False:
             # ---- update creator ----
             # Set the creator field to the current admin user
@@ -3255,8 +3251,8 @@ class PortfolioAdmin(ListHeaderAdmin):
         if is_federal and obj.organization_name is None:
             obj.organization_name = obj.federal_agency.agency
 
-        # TODO - this should be handled almost entirely in javascript
-        # Handle the federal agency and senior official fields
+        # Set the senior official field to the senior official on the federal agency
+        # when federal - otherwise, clear the field.
         if obj.organization_type == obj.OrganizationChoices.FEDERAL:
             if obj.federal_agency:
                 if obj.federal_agency.so_federal_agency.exists():
@@ -3269,7 +3265,6 @@ class PortfolioAdmin(ListHeaderAdmin):
                     obj.senior_official = None
                 obj.federal_agency = FederalAgency.objects.filter(agency="Non-Federal Agency").first()
 
-
         super().save_model(request, obj, form, change)
 
 
diff --git a/src/registrar/tests/test_admin.py b/src/registrar/tests/test_admin.py
index 9c5e3b582..2677462df 100644
--- a/src/registrar/tests/test_admin.py
+++ b/src/registrar/tests/test_admin.py
@@ -2103,6 +2103,66 @@ class TestPortfolioAdmin(TestCase):
         display_members = self.admin.display_members(self.portfolio)
         self.assertIn(f'<a href="{url}">2 members</a>', display_members)
 
+    @less_console_noise_decorator
+    def test_senior_official_readonly_for_federal_org(self):
+        """Test that senior_official field is readonly for federal organizations"""
+        request = self.factory.get("/")
+        request.user = self.superuser
+
+        # Create a federal portfolio
+        portfolio = Portfolio.objects.create(
+            organization_name="Test Federal Org",
+            organization_type=DomainRequest.OrganizationChoices.FEDERAL,
+            creator=self.superuser,
+        )
+
+        readonly_fields = self.admin.get_readonly_fields(request, portfolio)
+        self.assertIn("senior_official", readonly_fields)
+
+        # Change to non-federal org
+        portfolio.organization_type = DomainRequest.OrganizationChoices.CITY
+        readonly_fields = self.admin.get_readonly_fields(request, portfolio)
+        self.assertNotIn("senior_official", readonly_fields)
+
+    @less_console_noise_decorator
+    def test_senior_official_auto_assignment(self):
+        """Test automatic senior official assignment based on organization type and federal agency"""
+        request = self.factory.get("/")
+        request.user = self.superuser
+
+        # Create a federal agency with a senior official
+        federal_agency = FederalAgency.objects.create(agency="Test Agency")
+        senior_official = SeniorOfficial.objects.create(
+            first_name="Test",
+            last_name="Official",
+            title="Some guy",
+            email="test@example.gov",
+            federal_agency=federal_agency,
+        )
+
+        # Create a federal portfolio
+        portfolio = Portfolio.objects.create(
+            organization_name="Test Federal Org",
+            organization_type=DomainRequest.OrganizationChoices.FEDERAL,
+            creator=self.superuser,
+        )
+
+        # Test that the federal org gets senior official from agency when federal
+        portfolio.federal_agency = federal_agency
+        self.admin.save_model(request, portfolio, form=None, change=False)
+        self.assertEqual(portfolio.senior_official, senior_official)
+
+        # Test non-federal org clears senior official when not city
+        portfolio.organization_type = DomainRequest.OrganizationChoices.CITY
+        self.admin.save_model(request, portfolio, form=None, change=True)
+        self.assertIsNone(portfolio.senior_official)
+        self.assertEqual(portfolio.federal_agency.agency, "Non-Federal Agency")
+
+        # Cleanup
+        senior_official.delete()
+        federal_agency.delete()
+        portfolio.delete()
+
 
 class TestTransferUser(WebTest):
     """User transfer custom admin page"""