diff --git a/backend/src/db/migrations/20251021124744_fix-project-deletion-approval-policy-constraint.ts b/backend/src/db/migrations/20251021124744_fix-project-deletion-approval-policy-constraint.ts
new file mode 100644
index 000000000..88a38c6d6
--- /dev/null
+++ b/backend/src/db/migrations/20251021124744_fix-project-deletion-approval-policy-constraint.ts
@@ -0,0 +1,68 @@
+import { Knex } from "knex";
+
+import { TableName } from "../schemas";
+
+// Fix for 20250722152841_add-policies-environments-table.ts migration.
+// 20250722152841_add-policies-environments-table.ts introduced a bug where you can no longer delete a project if it has any approval policy environments.
+
+export async function up(knex: Knex): Promise<void> {
+  // Fix SecretApprovalPolicyEnvironment to cascade delete when environment is deleted
+  // note: this won't actually happen, as we prevent deletion of environments with active approval policies
+
+  // in the old migration it was ON DELETE SET NULL, which doesn't work because envId is not a nullable col
+  await knex.schema.alterTable(TableName.SecretApprovalPolicyEnvironment, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment).onDelete("CASCADE");
+  });
+
+  // Fix AccessApprovalPolicyEnvironment to cascade delete when environment is deleted
+  // note: this won't actually happen, as we prevent deletion of environments with active approval policies
+
+  // in the old migration it was ON DELETE SET NULL, which doesn't work because envId is not a nullable col
+  await knex.schema.alterTable(TableName.AccessApprovalPolicyEnvironment, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment).onDelete("CASCADE");
+  });
+
+  // Fix SecretApprovalPolicy to CASCADE instead of SET NULL
+
+  // in the old migration it was ON DELETE SET NULL, which doesn't work because envId is not a nullable col
+  await knex.schema.alterTable(TableName.SecretApprovalPolicy, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment).onDelete("CASCADE");
+  });
+
+  // Fix AccessApprovalPolicy to CASCADE instead of SET NULL
+
+  // in the old migration it was ON DELETE SET NULL, which doesn't work because envId is not a nullable col
+  await knex.schema.alterTable(TableName.AccessApprovalPolicy, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment).onDelete("CASCADE");
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  // Revert SecretApprovalPolicyEnvironment
+  await knex.schema.alterTable(TableName.SecretApprovalPolicyEnvironment, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment);
+  });
+
+  // Revert AccessApprovalPolicyEnvironment
+  await knex.schema.alterTable(TableName.AccessApprovalPolicyEnvironment, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment);
+  });
+
+  // Revert SecretApprovalPolicy back to SET NULL
+  await knex.schema.alterTable(TableName.SecretApprovalPolicy, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment).onDelete("SET NULL");
+  });
+
+  // Revert AccessApprovalPolicy back to SET NULL
+  await knex.schema.alterTable(TableName.AccessApprovalPolicy, (t) => {
+    t.dropForeign(["envId"]);
+    t.foreign("envId").references("id").inTable(TableName.Environment).onDelete("SET NULL");
+  });
+}