19 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 78613 | Cedar Park | 89,162 |
| 78665 | Round Rock | 64,087 |
| 78664 | Round Rock | 62,272 |
| 78681 | Round Rock | 58,531 |
| 78626 | Georgetown | 45,020 |
| 78628 | Georgetown | 44,821 |
| 78634 | Hutto | 43,466 |
| 78717 | Austin | 36,085 |
| 78729 | Austin | 30,440 |
| 78633 | Georgetown | 28,877 |
| 78642 | Liberty Hill | 24,146 |
| 76574 | Taylor | 19,746 |
| 76537 | Jarrell | 12,526 |
| 76527 | Florence | 4,686 |
| 76530 | Granger | 2,704 |
| 76578 | Thrall | 1,561 |
| 78615 | Coupland | 1,540 |
| 78674 | Weir | 195 |
| 76573 | Schwertner | 22 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 19 ZCTAs in Williamson County, Texas (US Census).