diff --git a/django/thunderstore/repository/package_manifest.py b/django/thunderstore/repository/package_manifest.py
index 0eeca6c94..70107c103 100644
--- a/django/thunderstore/repository/package_manifest.py
+++ b/django/thunderstore/repository/package_manifest.py
@@ -13,7 +13,11 @@
     PackageVersionField,
     StrictCharField,
 )
-from thunderstore.repository.utils import does_contain_package, has_duplicate_packages
+from thunderstore.repository.utils import (
+    does_contain_package,
+    has_different_case,
+    has_duplicate_packages,
+)
 
 
 class PackageInstallerSerializer(serializers.Serializer):
@@ -96,6 +100,10 @@ def validate(self, data):
             )
         if does_contain_package(result["dependencies"], reference):
             raise ValidationError("Package depending on itself is not allowed")
+        if has_different_case(reference.without_version):
+            raise ValidationError(
+                "Package name already exists with different capitalization"
+            )
         return result
 
     def update(self, instance, validated_data):
diff --git a/django/thunderstore/repository/package_reference.py b/django/thunderstore/repository/package_reference.py
index 98e75c0b6..f6233a81f 100644
--- a/django/thunderstore/repository/package_reference.py
+++ b/django/thunderstore/repository/package_reference.py
@@ -257,3 +257,22 @@ def exists(self) -> bool:
         :rtype: bool
         """
         return self.queryset.exists()
+
+    @cached_property
+    def exists_in_any_case(self) -> bool:
+        """
+        Check if a package with a name with different capitalization exists in the db
+
+        :return: True if a different case package exists, False otherwise
+        :rtype: bool
+        """
+        if self.version:
+            return Package.objects.filter(
+                package__owner__name=self.namespace,
+                package__name__iexact=self.name,
+                version_number=self.version_str,
+            ).exists()
+        else:
+            return Package.objects.filter(
+                owner__name=self.namespace, name__iexact=self.name
+            ).exists()
diff --git a/django/thunderstore/repository/tests/test_package_manifest.py b/django/thunderstore/repository/tests/test_package_manifest.py
index 45beb333f..9808a80de 100644
--- a/django/thunderstore/repository/tests/test_package_manifest.py
+++ b/django/thunderstore/repository/tests/test_package_manifest.py
@@ -55,6 +55,28 @@ def test_manifest_v1_serializer_version_already_exists(
     )
 
 
+@pytest.mark.django_db
+def test_manifest_v1_serializer_package_already_exists_with_different_case(
+    user, manifest_v1_data, package
+):
+    TeamMember.objects.create(
+        user=user,
+        team=package.owner,
+        role=TeamMemberRole.owner,
+    )
+    manifest_v1_data["name"] = package.name.swapcase()
+    serializer = ManifestV1Serializer(
+        user=user,
+        team=package.owner,
+        data=manifest_v1_data,
+    )
+    assert serializer.is_valid() is False
+    assert len(serializer.errors["non_field_errors"]) == 1
+    assert "Package name already exists with different capitalization" in str(
+        serializer.errors["non_field_errors"][0]
+    )
+
+
 @pytest.mark.django_db
 def test_manifest_v1_serializer_duplicate_dependency(
     user, manifest_v1_data, package_version, namespace
diff --git a/django/thunderstore/repository/utils.py b/django/thunderstore/repository/utils.py
index 0fb669594..b643c08a8 100644
--- a/django/thunderstore/repository/utils.py
+++ b/django/thunderstore/repository/utils.py
@@ -42,6 +42,14 @@ def has_duplicate_packages(packages: List["PackageReference"]) -> bool:
     return False
 
 
+def has_different_case(reference: "PackageReference") -> bool:
+    if reference.exists:
+        return False
+    elif reference.exists_in_any_case:
+        return True
+    return False
+
+
 def unpack_serializer_errors(field, errors, error_dict=None):
     if error_dict is None:
         error_dict = {}