Post Offices List in Ontario City, California:
| Ontario Post Office | 1555 E Holt Blvd, Ontario, CA 91761 |
| Plaza Center Post Office | 1126 N Mountain Ave, Ontario, CA 91762 |
| Downtown Ontario Post Office | 123 W Holt Blvd, Ontario, CA 91762 |
| Ontario Post Office | 1555 E Holt Blvd, Ontario, CA 91761 |
| Plaza Center Post Office | 1126 N Mountain Ave, Ontario, CA 91762 |
| Downtown Ontario Post Office | 123 W Holt Blvd, Ontario, CA 91762 |