| Zip Code | City | Population ↓ |
|---|---|---|
| 7083 | Union | 56,900 |
| 7060 | Plainfield | 47,883 |
| 7036 | Linden | 44,996 |
| 7202 | Elizabeth | 44,673 |
| 7208 | Elizabeth | 32,632 |
| 7090 | Westfield | 30,852 |
| 7206 | Elizabethport | 30,364 |
| 7065 | Rahway | 29,664 |
| 7201 | Elizabeth | 27,996 |
| 7076 | Scotch Plains | 24,727 |
| 7901 | Summit | 24,281 |
| 7016 | Cranford | 23,838 |
| 7203 | Roselle | 22,500 |
| 7205 | Hillside | 22,262 |
| 7081 | Springfield | 17,011 |
| 7066 | Clark | 15,415 |
| 7063 | Plainfield | 14,849 |
| 7062 | Plainfield | 14,253 |
| 7204 | Roselle Park | 13,964 |
| 7974 | New Providence | 12,911 |
| 7922 | Berkeley Heights | 12,078 |
| 7033 | Kenilworth | 8,345 |
| 7023 | Fanwood | 7,723 |
| 7092 | Mountainside | 6,991 |
| 7027 | Garwood | 4,542 |
| 7088 | Vauxhall | 3,056 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 26 ZCTAs in Union County, New Jersey (US Census).