19 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 78613 | Cedar Park | 88,189 |
| 78664 | Round Rock | 62,168 |
| 78665 | Round Rock | 61,640 |
| 78681 | Round Rock | 57,760 |
| 78628 | Georgetown | 41,428 |
| 78634 | Hutto | 41,099 |
| 78626 | Georgetown | 40,758 |
| 78717 | Austin | 34,499 |
| 78729 | Austin | 31,309 |
| 78633 | Georgetown | 27,292 |
| 78642 | Liberty Hill | 20,699 |
| 76574 | Taylor | 19,629 |
| 76537 | Jarrell | 11,501 |
| 76527 | Florence | 4,141 |
| 76530 | Granger | 2,424 |
| 78615 | Coupland | 1,781 |
| 76578 | Thrall | 1,232 |
| 78674 | Weir | 233 |
| 76573 | Schwertner | 27 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 19 ZCTAs in Williamson County, Texas (US Census).