| # | Company name | Role | # of projects |
|---|---|---|---|
| 41 | Concord Engineering | MEP engineering | 1 |
| 42 | Conseil Plus Ingénierie | MEP engineering | 3 |
| 43 | Consolidated Consulting Engineers | MEP engineering | 7 |
| 44 | Consolidated Consulting Engineers Limited | MEP engineering | 8 |
| 45 | Consulting Engineering Group, Inc., International | MEP engineering | 2 |
| 46 | Cosentini Associates | MEP engineering | 212 |
| 47 | Cosentini Associates | MEP engineering | 16 |
| 48 | Cosentini Associates | MEP engineering | 19 |
| 49 | COWI Baltic UAB | MEP engineering | 7 |
| 50 | Crawford Williams Engineering, Inc. | MEP engineering | 8 |
| 51 | Creanova AB | MEP engineering | 4 |
| 52 | Crespo y Blasco S.A. | MEP engineering | 3 |
| 53 | Crossey Engineering Ltd. | MEP engineering | 4 |
| 54 | CTH | MEP engineering | 2 |
| 55 | Cundall | MEP engineering | 2 |