| # | Company name | Role | # of projects |
|---|---|---|---|
| 1 | Caja Madrid | Owner | 4 |
| 2 | Calter Ingeniería S.L. | Engineering company | 1 |
| 3 | Carlos Arroyo Arquitectos | Architect | 1 |
| 4 | Carmen Bravo Durá | Architect | 0 |
| 5 | Cartera Meridional S.A. | Real estate agent | 0 |
| 6 | Casas y Casas | Architect | 1 |
| 7 | CB Richard Ellis España | Real estate agent | 20 |
| 8 | CEMEX España | Concrete supplier | 3 |
| 9 | Chapman Taylor España | Architect | 3 |
| 10 | Cimenfor | Foundation company | 0 |
| 11 | Cintra | Parking management | 5 |
| 12 | Comunidad de Madrid (Environment and Territorial Planning Department) | Business development | 1 |
| 13 | Comunidades Castellana | Developer | 3 |
| 14 | Construcciones San Martin | Construction company | 5 |
| 15 | Construcciones y Promociones Coprosa S.A. | Construction company | 4 |
| 16 | Cooperativa de Clientes Monte Aralar | Client | 5 |
| 17 | Cooperativa de Viviendas Vecope | Developer | 0 |
| 18 | Copasa, S.A. de Obras y Servicios | Construction company | 0 |
| 19 | Crespo y Blasco S.A. | MEP engineering | 3 |
| 20 | Cubic Real Estate S.L. | Real estate agent | 0 |