diff --git a/src/registrar/admin.py b/src/registrar/admin.py
index 5b88a9ce2..0096f59b5 100644
--- a/src/registrar/admin.py
+++ b/src/registrar/admin.py
@@ -16,7 +16,7 @@ from django.urls import reverse
 from dateutil.relativedelta import relativedelta  # type: ignore
 from epplibwrapper.errors import ErrorCode, RegistryError
 from registrar.models import Contact, Domain, DomainRequest, DraftDomain, User, Website
-from registrar.utility.errors import FSMApplicationError, FSMErrorCodes
+from registrar.utility.errors import FSMDomainRequestError, FSMErrorCodes
 from registrar.views.utility.mixins import OrderableFieldsMixin
 from django.contrib.admin.views.main import ORDER_VAR
 from registrar.widgets import NoAutocompleteFilteredSelectMultiple
@@ -133,6 +133,7 @@ class DomainRequestAdminForm(forms.ModelForm):
         cleaned_data = super().clean()
         status = cleaned_data.get("status")
         investigator = cleaned_data.get("investigator")
+        rejection_reason = cleaned_data.get("rejection_reason")
 
         # Get the old status
         initial_status = self.initial.get("status", None)
@@ -153,8 +154,32 @@ class DomainRequestAdminForm(forms.ModelForm):
             # Will call "add_error" if any issues are found.
             self._check_for_valid_investigator(investigator)
 
+        # If the status is rejected, a rejection reason must exist
+        if status == DomainRequest.DomainRequestStatus.REJECTED:
+            self._check_for_valid_rejection_reason(rejection_reason)
+
         return cleaned_data
 
+    def _check_for_valid_rejection_reason(self, rejection_reason) -> bool:
+        """
+        Checks if the rejection_reason field is not none.
+        Adds form errors on failure.
+        """
+        is_valid = False
+
+        # Check if a rejection reason exists. Rejection is not possible without one.
+        error_message = None
+        if rejection_reason is None or rejection_reason == "":
+            # Lets grab the error message from a common location
+            error_message = FSMDomainRequestError.get_error_message(FSMErrorCodes.NO_REJECTION_REASON)
+        else:
+            is_valid = True
+
+        if error_message is not None:
+            self.add_error("rejection_reason", error_message)
+
+        return is_valid
+
     def _check_for_valid_investigator(self, investigator) -> bool:
         """
         Checks if the investigator field is not none, and is staff.
@@ -167,9 +192,9 @@ class DomainRequestAdminForm(forms.ModelForm):
         error_message = None
         if investigator is None:
             # Lets grab the error message from a common location
-            error_message = FSMApplicationError.get_error_message(FSMErrorCodes.NO_INVESTIGATOR)
+            error_message = FSMDomainRequestError.get_error_message(FSMErrorCodes.NO_INVESTIGATOR)
         elif not investigator.is_staff:
-            error_message = FSMApplicationError.get_error_message(FSMErrorCodes.INVESTIGATOR_NOT_STAFF)
+            error_message = FSMDomainRequestError.get_error_message(FSMErrorCodes.INVESTIGATOR_NOT_STAFF)
         else:
             is_valid = True
 
@@ -994,7 +1019,7 @@ class DomainRequestAdmin(ListHeaderAdmin):
             if self.value() == "0":
                 return queryset.filter(Q(is_election_board=False) | Q(is_election_board=None))
 
-    change_form_template = "django/admin/domain_application_change_form.html"
+    change_form_template = "django/admin/domain_request_change_form.html"
 
     # Columns
     list_display = [
@@ -1209,7 +1234,7 @@ class DomainRequestAdmin(ListHeaderAdmin):
             # This condition should never be triggered.
             # The opposite of this condition is acceptable (rejected -> other status and rejection_reason)
             # because we clean up the rejection reason in the transition in the model.
-            error_message = "A rejection reason is required."
+            error_message = FSMDomainRequestError.get_error_message(FSMErrorCodes.NO_REJECTION_REASON)
         else:
             # This is an fsm in model which will throw an error if the
             # transition condition is violated, so we roll back the
@@ -1218,11 +1243,11 @@ class DomainRequestAdmin(ListHeaderAdmin):
             obj.status = original_obj.status
 
             # Try to perform the status change.
-            # Catch FSMApplicationError's and return the message,
+            # Catch FSMDomainRequestError's and return the message,
             # as these are typically user errors.
             try:
                 selected_method()
-            except FSMApplicationError as err:
+            except FSMDomainRequestError as err:
                 logger.warning(f"An error encountered when trying to change status: {err}")
                 error_message = err.message
 
diff --git a/src/registrar/assets/sass/_theme/_admin.scss b/src/registrar/assets/sass/_theme/_admin.scss
index 18025a9cb..b7a494aef 100644
--- a/src/registrar/assets/sass/_theme/_admin.scss
+++ b/src/registrar/assets/sass/_theme/_admin.scss
@@ -346,3 +346,7 @@ input.admin-confirm-button {
 .usa-summary-box__dhs-color {
     color: $dhs-blue-70;
 }
+
+.errors span.select2-selection {
+    border: 1px solid var(--error-fg) !important;
+}
\ No newline at end of file
diff --git a/src/registrar/models/domain_request.py b/src/registrar/models/domain_request.py
index 7527529a1..f4581de93 100644
--- a/src/registrar/models/domain_request.py
+++ b/src/registrar/models/domain_request.py
@@ -9,7 +9,7 @@ from django.db import models
 from django_fsm import FSMField, transition  # type: ignore
 from django.utils import timezone
 from registrar.models.domain import Domain
-from registrar.utility.errors import FSMApplicationError, FSMErrorCodes
+from registrar.utility.errors import FSMDomainRequestError, FSMErrorCodes
 
 from .utility.time_stamped_model import TimeStampedModel
 from ..utility.email import send_templated_email, EmailSendingError
@@ -791,7 +791,7 @@ class DomainRequest(TimeStampedModel):
 
         # == Check that the domain_request is valid == #
         if Domain.objects.filter(name=self.requested_domain.name).exists():
-            raise FSMApplicationError(code=FSMErrorCodes.APPROVE_DOMAIN_IN_USE)
+            raise FSMDomainRequestError(code=FSMErrorCodes.APPROVE_DOMAIN_IN_USE)
 
         # == Create the domain and related components == #
         created_domain = Domain.objects.create(name=self.requested_domain.name)
diff --git a/src/registrar/templates/django/admin/domain_application_change_form.html b/src/registrar/templates/django/admin/domain_request_change_form.html
similarity index 100%
rename from src/registrar/templates/django/admin/domain_application_change_form.html
rename to src/registrar/templates/django/admin/domain_request_change_form.html
diff --git a/src/registrar/tests/test_admin.py b/src/registrar/tests/test_admin.py
index 28a500ae2..8ed61d76c 100644
--- a/src/registrar/tests/test_admin.py
+++ b/src/registrar/tests/test_admin.py
@@ -555,6 +555,24 @@ class TestDomainRequestAdminForm(TestCase):
             expected_choices = [("started", "Started"), ("submitted", "Submitted")]
             self.assertEqual(form.fields["status"].widget.choices, expected_choices)
 
+    def test_form_no_rejection_reason(self):
+        with less_console_noise():
+            # Create a form instance with the test domain request
+            form = DomainRequestAdminForm(instance=self.domain_request)
+
+            form = DomainRequestAdminForm(
+                instance=self.domain_request,
+                data={
+                    "status": DomainRequest.DomainRequestStatus.REJECTED,
+                    "rejection_reason": None,
+                },
+            )
+            self.assertFalse(form.is_valid())
+            self.assertIn("rejection_reason", form.errors)
+
+            rejection_reason = form.errors.get("rejection_reason")
+            self.assertEqual(rejection_reason, ["A rejection reason is required."])
+
     def test_form_choices_when_no_instance(self):
         with less_console_noise():
             # Create a form instance without an instance
diff --git a/src/registrar/utility/errors.py b/src/registrar/utility/errors.py
index 00c65ce57..f00c59bd0 100644
--- a/src/registrar/utility/errors.py
+++ b/src/registrar/utility/errors.py
@@ -78,15 +78,17 @@ class FSMErrorCodes(IntEnum):
         - 2 NO_INVESTIGATOR No investigator is assigned
         - 3 INVESTIGATOR_NOT_STAFF Investigator is a non-staff user
         - 4 INVESTIGATOR_NOT_SUBMITTER The form submitter is not the investigator
+        - 5 NO_REJECTION_REASON No rejection reason is specified
     """
 
     APPROVE_DOMAIN_IN_USE = 1
     NO_INVESTIGATOR = 2
     INVESTIGATOR_NOT_STAFF = 3
     INVESTIGATOR_NOT_SUBMITTER = 4
+    NO_REJECTION_REASON = 5
 
 
-class FSMApplicationError(Exception):
+class FSMDomainRequestError(Exception):
     """
     Used to raise exceptions when doing FSM Transitions.
     Uses `FSMErrorCodes` as an enum.
@@ -97,6 +99,7 @@ class FSMApplicationError(Exception):
         FSMErrorCodes.NO_INVESTIGATOR: ("Investigator is required for this status."),
         FSMErrorCodes.INVESTIGATOR_NOT_STAFF: ("Investigator is not a staff user."),
         FSMErrorCodes.INVESTIGATOR_NOT_SUBMITTER: ("Only the assigned investigator can make this change."),
+        FSMErrorCodes.NO_REJECTION_REASON: ("A rejection reason is required."),
     }
 
     def __init__(self, *args, code=None, **kwargs):