diff --git a/packages/orm/src/client/crud/dialects/postgresql.ts b/packages/orm/src/client/crud/dialects/postgresql.ts
index 733af920c..92e570fe8 100644
--- a/packages/orm/src/client/crud/dialects/postgresql.ts
+++ b/packages/orm/src/client/crud/dialects/postgresql.ts
@@ -22,6 +22,7 @@ import {
     getDelegateDescendantModels,
     getManyToManyRelation,
     isRelationField,
+    isTypeDef,
     requireField,
     requireIdFields,
     requireModel,
@@ -52,13 +53,25 @@ export class PostgresCrudDialect<Schema extends SchemaDef> extends BaseCrudDiale
             invariant(false, 'should not reach here: AnyNull is not a valid input value');
         }
 
-        if (Array.isArray(value)) {
+        // node-pg incorrectly handles array values passed to non-array JSON fields,
+        // the workaround is to JSON stringify the value
+        // https://github.com/brianc/node-postgres/issues/374
+
+        if (isTypeDef(this.schema, type)) {
+            // type-def fields (regardless array or scalar) are stored as scalar `Json` and
+            // their input values need to be stringified if not already (i.e., provided in
+            // default values)
+            if (typeof value !== 'string') {
+                return JSON.stringify(value);
+            } else {
+                return value;
+            }
+        } else if (Array.isArray(value)) {
             if (type === 'Json' && !forArrayField) {
-                // node-pg incorrectly handles array values passed to non-array JSON fields,
-                // the workaround is to JSON stringify the value
-                // https://github.com/brianc/node-postgres/issues/374
+                // scalar `Json` fields need their input stringified
                 return JSON.stringify(value);
             } else {
+                // `Json[]` fields need their input as array (not stringified)
                 return value.map((v) => this.transformPrimitive(v, type, false));
             }
         } else {
diff --git a/tests/regression/test/issue-493.test.ts b/tests/regression/test/issue-493.test.ts
new file mode 100644
index 000000000..269a68f33
--- /dev/null
+++ b/tests/regression/test/issue-493.test.ts
@@ -0,0 +1,94 @@
+import { createTestClient } from '@zenstackhq/testtools';
+import { describe, expect, it } from 'vitest';
+
+describe('Issue 493 regression tests', () => {
+    it('should correctly handle JSON and typed-JSON array fields for PostgreSQL', async () => {
+        const schema = `
+type InlineButton {
+    id            String
+    text          String
+    callback_data String?
+    url           String?
+    message       String?
+    type          String?
+}
+
+type BotButton {
+    id             String
+    label          String
+    action         String
+    enabled        Boolean
+    order_index    Int
+    message        String
+    inline_buttons InlineButton[]?  // Nested custom type
+}
+
+model bot_settings {
+    id           Int         @id @default(autoincrement())
+    setting_key  String      @unique
+    menu_buttons BotButton[] @json  // Array of custom type
+    meta         Meta        @json
+}
+
+type Meta {
+    info String
+}
+
+model Foo {
+    id   Int  @id @default(autoincrement())
+    data Json
+}
+`;
+
+        const db = await createTestClient(schema, { provider: 'postgresql', debug: true });
+
+        // plain JSON non-array
+        await expect(
+            db.foo.create({
+                data: {
+                    data: { hello: 'world' },
+                },
+            }),
+        ).resolves.toMatchObject({
+            data: { hello: 'world' },
+        });
+
+        // plain JSON array
+        await expect(
+            db.foo.create({
+                data: {
+                    data: [{ hello: 'world' }],
+                },
+            }),
+        ).resolves.toMatchObject({
+            data: [{ hello: 'world' }],
+        });
+
+        // typed-JSON array & non-array
+        const input = {
+            setting_key: 'abc',
+            menu_buttons: [
+                {
+                    id: '1',
+                    label: 'Button 1',
+                    action: 'action_1',
+                    enabled: true,
+                    order_index: 1,
+                    message: 'msg',
+                    inline_buttons: [
+                        {
+                            id: 'ib1',
+                            text: 'Inline 1',
+                        },
+                    ],
+                },
+            ],
+            meta: { info: 'some info' },
+        };
+        await expect(
+            db.bot_settings.create({
+                data: input,
+            }),
+        ).resolves.toMatchObject(input);
+    });
+});