The canton Saint-Omer has 16 communes.
| Code | Name | Population ▼ |
|---|---|---|
| 62765 | Saint-Omer | 14 382 |
| 62757 | Saint-Martin-lez-Tatinghem | 5 843 |
| 62297 | Éperlecques | 3 737 |
| 62827 | Tournehem-sur-la-Hem | 1 376 |
| 62618 | Nordausques | 1 271 |
| 62792 | Serques | 1 210 |
| 62595 | Moulle | 1 170 |
| 62458 | Houlle | 1 116 |
| 62819 | Tilques | 1 072 |
| 62087 | Bayenghem-lès-Éperlecques | 1 018 |
| 62567 | Mentque-Nortbécourt | 649 |
| 62225 | Clairmarais | 593 |
| 62904 | Zouafques | 592 |
| 62592 | Moringhem | 557 |
| 62772 | Salperwick | 521 |
| 62622 | Nort-Leulinghem | 261 |