| Postal Code | Town | County |
|---|---|---|
| 20503 | Olololunga | Narok |
| 20507 | Oloomirani | Narok |
| 20424 | Oloomirani | Narok |
| 00213 | Oltepesi | Kajiado |
| 40306 | Omboga | Homa Bay |
| 40221 | Omogonchoro | Kisii |
| 40111 | Onditi | Kisumu |
| 00511 | Ongata Rongai | Kajiado |
| 40227 | Oriang | Homa Bay |
| 30602 | Ortum | West Pokot |