diff --git a/backend/src/db/migrations/20251023121055_fix-missing-group-memberships.ts b/backend/src/db/migrations/20251023121055_fix-missing-group-memberships.ts
new file mode 100644
index 000000000..56fe82b2c
--- /dev/null
+++ b/backend/src/db/migrations/20251023121055_fix-missing-group-memberships.ts
@@ -0,0 +1,60 @@
+import { Knex } from "knex";
+
+import { AccessScope, TableName } from "../schemas";
+
+export async function up(knex: Knex): Promise<void> {
+  const hasGroupsTable = await knex.schema.hasTable(TableName.Groups);
+  const hasMembershipTable = await knex.schema.hasTable(TableName.Membership);
+  const hasMembershipRoleTable = await knex.schema.hasTable(TableName.MembershipRole);
+
+  if (!hasGroupsTable || !hasMembershipTable || !hasMembershipRoleTable) {
+    return;
+  }
+
+  const groupsWithoutMembership = await knex
+    .select(
+      `${TableName.Groups}.id`,
+      `${TableName.Groups}.orgId`,
+      `${TableName.Groups}.role`,
+      `${TableName.Groups}.roleId`
+    )
+    .from(TableName.Groups)
+    .leftJoin(TableName.Membership, `${TableName.Groups}.id`, `${TableName.Membership}.actorGroupId`)
+    .whereNull(`${TableName.Membership}.actorGroupId`);
+
+  if (groupsWithoutMembership.length > 0) {
+    const membershipInserts = groupsWithoutMembership.map((group) => ({
+      actorGroupId: group.id,
+      scope: AccessScope.Organization,
+      scopeOrgId: group.orgId,
+      isActive: true
+    }));
+
+    const insertedMemberships = await knex(TableName.Membership).insert(membershipInserts).returning("*");
+
+    const membershipRoleInserts = insertedMemberships.map((membership, index) => {
+      const group = groupsWithoutMembership[index];
+      return {
+        membershipId: membership.id,
+        role: group.role,
+        customRoleId: group.roleId
+      };
+    });
+
+    await knex(TableName.MembershipRole).insert(membershipRoleInserts);
+  }
+
+  await knex.schema.alterTable(TableName.Membership, (t) => {
+    t.check(
+      `("actorUserId" IS NOT NULL OR "actorIdentityId" IS NOT NULL OR "actorGroupId" IS NOT NULL)`,
+      undefined,
+      "at_least_one_actor"
+    );
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  await knex.schema.alterTable(TableName.Membership, (t) => {
+    t.dropChecks("at_least_one_actor");
+  });
+}
diff --git a/backend/src/ee/services/saml-config/saml-config-service.ts b/backend/src/ee/services/saml-config/saml-config-service.ts
index 13b862343..c99ae8b28 100644
--- a/backend/src/ee/services/saml-config/saml-config-service.ts
+++ b/backend/src/ee/services/saml-config/saml-config-service.ts
@@ -84,7 +84,7 @@ type TSamlConfigServiceFactoryDep = {
   projectDAL: Pick<TProjectDALFactory, "findById" | "findProjectGhostUser">;
   projectBotDAL: Pick<TProjectBotDALFactory, "findOne">;
   projectKeyDAL: Pick<TProjectKeyDALFactory, "find" | "delete" | "findLatestProjectKey" | "insertMany">;
-  membershipGroupDAL: Pick<TMembershipGroupDALFactory, "find">;
+  membershipGroupDAL: Pick<TMembershipGroupDALFactory, "find" | "create">;
 };
 
 export const samlConfigServiceFactory = ({
@@ -183,6 +183,22 @@ export const samlConfigServiceFactory = ({
             transaction
           );
           orgGroupsMap.set(groupName, newGroup);
+          const orgMembership = await membershipGroupDAL.create(
+            {
+              actorGroupId: newGroup.id,
+              scope: AccessScope.Organization,
+              scopeOrgId: orgId
+            },
+            transaction
+          );
+          await membershipRoleDAL.create(
+            {
+              membershipId: orgMembership.id,
+              role: OrgMembershipRole.NoAccess,
+              customRoleId: null
+            },
+            transaction
+          );
         }
       }