| # | Company name | Role | # of projects |
|---|---|---|---|
| 1 | H & H Building Consultants, Inc. | Consultancy | 2 |
| 2 | H C Nutting Company | Consultancy | 1 |
| 3 | H D R Engineers | Consultancy | 0 |
| 4 | H H Holmes Laboratories Inc | Consultancy | 1 |
| 5 | H. R. Gray & Associates, Inc. | Consultancy | 0 |
| 6 | H. R. Gray & Associates, Inc. | Consultancy | 0 |
| 7 | H.H. Angus & Associates Limited | Consultancy | 1 |
| 8 | H2 Consulting P.E.P.C. | Consultancy | 2 |
| 9 | H2m Labs Inc. | Consultancy | 0 |
| 10 | Hackworth Reprographics Inc. | Consultancy | 0 |
| 11 | Hagoplan Engineering | Consultancy | 0 |
| 12 | Hai-vinh Ly & Associates | Consultancy | 1 |
| 13 | Halcrow Group Ltd. | Consultancy | 12 |
| 14 | Hale Allen Jones | Consultancy | 1 |
| 15 | HALI Büromöbel GmbH | Consultancy | 1 |
| 16 | Hammes Company Sports & Entertainment | Consultancy | 3 |
| 17 | Hammond & Associates | Consultancy | 2 |
| 18 | Han-padron Associates | Consultancy | 1 |
| 19 | Hanover Cube | Consultancy | 4 |
| 20 | Hanscomb Associates | Consultancy | 1 |