diff --git a/src/registrar/forms/domain_request_wizard.py b/src/registrar/forms/domain_request_wizard.py
index eed0866f3..d84ceeb15 100644
--- a/src/registrar/forms/domain_request_wizard.py
+++ b/src/registrar/forms/domain_request_wizard.py
@@ -90,7 +90,7 @@ class RequestingEntityForm(RegistrarForm):
             raise ValidationError(
                 "This suborganization already exists. "
                 "Choose a new name, or select it directly if you would like to use it."
-            )
+        )
         return name
 
     def full_clean(self):
diff --git a/src/registrar/models/domain_request.py b/src/registrar/models/domain_request.py
index c0d4c7e57..ff3af829b 100644
--- a/src/registrar/models/domain_request.py
+++ b/src/registrar/models/domain_request.py
@@ -672,6 +672,46 @@ class DomainRequest(TimeStampedModel):
         # Store original values for caching purposes. Used to compare them on save.
         self._cache_status_and_status_reasons()
 
+    def clean(self):
+        super().clean()
+        # Validation logic for a suborganization request
+        if self.is_requesting_new_suborganization():
+            # Raise an error if this suborganization already exists
+            Suborganization = apps.get_model("registrar.Suborganization")
+            if (
+                self.requested_suborganization
+                and Suborganization.objects.filter(
+                    name__iexact=self.requested_suborganization,
+                    portfolio=self.portfolio,
+                    name__isnull=False,
+                    portfolio__isnull=False,
+                ).exists()
+            ):
+                raise ValidationError(
+                    "This suborganization already exists. "
+                    "Choose a new name, or select it directly if you would like to use it."
+                )
+        elif self.portfolio and not self.sub_organization:
+            # You cannot create a new suborganization without these fields
+            required_suborg_fields = {
+                "requested_suborganization": self.requested_suborganization,
+                "suborganization_city": self.suborganization_city,
+                "suborganization_state_territory": self.suborganization_state_territory,
+            }
+
+            if any(bool(value) for value in required_suborg_fields.values()):
+                # Find which fields are empty
+                errors_dict = {
+                    field_name: [f"This field is required when creating a new suborganization."]
+                    for field_name, value in required_suborg_fields.items()
+                    if not value
+                }
+                # Adds a validation error to each missing field
+                raise ValidationError({
+                    k: ValidationError(v, code='required')
+                    for k, v in errors_dict.items()
+                })
+
     def save(self, *args, **kwargs):
         """Save override for custom properties"""
         self.sync_organization_type()
diff --git a/src/registrar/models/suborganization.py b/src/registrar/models/suborganization.py
index 087490244..78689799c 100644
--- a/src/registrar/models/suborganization.py
+++ b/src/registrar/models/suborganization.py
@@ -1,5 +1,4 @@
 from django.db import models
-
 from registrar.models.domain_request import DomainRequest
 from .utility.time_stamped_model import TimeStampedModel