The canton Grand-Champ has 17 communes.
| Code | Name | Population ▼ |
|---|---|---|
| 56067 | Grand-Champ | 5 929 |
| 56117 | Locminé | 4 773 |
| 56144 | Évellys | 3 379 |
| 56174 | Plumelin | 2 885 |
| 56024 | Bréhan | 2 306 |
| 56042 | Colpo | 2 296 |
| 56120 | Locqueltas | 2 031 |
| 56157 | Plaudren | 1 978 |
| 56190 | Réguiny | 1 955 |
| 56115 | Locmaria-Grand-Champ | 1 855 |
| 56141 | Moustoir-Ac | 1 775 |
| 56198 | Rohan | 1 526 |
| 56047 | Crédin | 1 483 |
| 56022 | Brandivy | 1 466 |
| 56160 | Pleugriffet | 1 281 |
| 56189 | Radenac | 1 066 |
| 56039 | La Chapelle-Neuve | 1 001 |