| Imperial Plumbing | Imperial Plumbing | — | (925) 481 1929 | Other | Concord · Contra Costa County | — | — |
| Impressive Plumbing | Impressive Plumbing | — | (415) 797 0246 | Other | Hercules · Contra Costa County | — | — |
| In Compliance Engineering Services | Lucas Joseph Jones | — | (925) 852 9827 | Other | Bethel Island · Contra Costa County | — | — |
| In Demand Plumbing Heating & Air INC | Jeffery Ryan Clinkenbeard | — | (925) 757 7000 | HVAC | Antioch · Contra Costa County | — | — |
| In Focus Low Voltage Services | Macias Negrete Ery | — | (925) 550 1128 | Other | Concord · Contra Costa County | — | — |
| In'contempo Builders & Design INC | Josef William Kosla | — | (415) 424 3245 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| In-depth Leak Detection LLC | Gene Lee Pullin | — | (925) 934 1500 | Pool | Concord · Contra Costa County | — | — |
| Independent Plumbing | Independent Plumbing | impallari@gmail.com | (925) 567 6503 | Other | Concord · Contra Costa County | — | — |
| Indian Sunny Builders | Indian Sunny Builders | — | (925) 382 5324 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Industrial Battery Services | Francisco Feliciano Recoder | — | (510) 412 5980 | Electricians | Richmond · Contra Costa County | — | — |
| Infinite Construction | Huy Van Huynh | — | (415) 438 0042 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| Infiniti Hardwood Floors | Infiniti Hardwood Floors | — | (925) 765 1232 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Infinity HVAC Services Corp | Osnat Fahima | — | (415) 412 4573 | HVAC | Brentwood · Contra Costa County | — | — |
| Infinium Air INC | Neven Kalas | — | (925) 826 5180 | HVAC | Concord · Contra Costa County | — | — |
| Ingenious General Construction | Juan Carlos Vargas | — | (925) 848 7043 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Ingram Construction Incorporated | Vincent Brian Ingram | — | (925) 383 2056 | GC, remodel, ADU | Clayton · Contra Costa County | — | — |
| Ingram Painting | Ingram Painting | — | (510) 302 5681 | Windows, patio, painters | Pinole · Contra Costa County | — | — |
| Innova Builders Ca INC | Shaul Shawn Arbib | — | (510) 406 6020 | GC, remodel, ADU | Orinda · Contra Costa County | — | — |
| Innovation Glass & Windows | Ayala Alecxi Camacho | — | (415) 532 9426 | Windows, patio, painters | San Pablo · Contra Costa County | — | — |
| Innovation Hardwood Floor Company | Ronny Orlando Fajardo | — | (510) 260 6620 | Other | San Pablo · Contra Costa County | — | — |
| Innovation Home Remodels | Manuel Telesforo Aguilera | — | (925) 497 3407 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Innovation Roofing System | Hernandez Pereira Marcos | — | (510) 330 3834 | Other roofers | Antioch · Contra Costa County | — | — |
| Innovative Accents | Innovative Accents | — | (925) 525 1311 | Windows, patio, painters | Clayton · Contra Costa County | — | — |
| Innovative Communication Technology INC | Joselito Lagman Cruz | — | (925) 349 2400 | Other | Concord · Contra Costa County | — | — |
| Innovative Painting | Jose Rosendo Guzman Sanchez | — | (925) 864 9202 | Windows, patio, painters | Pittsburg · Contra Costa County | — | — |
| Innovative Tile | Innovative Tile | — | (510) 407 8079 | Other | El Cerrito · Contra Costa County | — | — |
| Inovi INC | Inderpreet Singh Dhanoa | — | (415) 841 3226 | Other | Moraga · Contra Costa County | — | — |
| Insite Design & Build INC | Christopher John Simoneaux | — | (925) 689 6460 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Inspirada Group | Jimenez Ivan | — | (510) 513 7732 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| Insul - Techs INC | Luis Ernesto| Ramos Luis Ramos Cortez | info@insultechs.com | (925) 595 8020 | Other | Concord · Contra Costa County | — | — |
| Intech | Salvador Jordan Sanchez | — | (415) 900 6600 | Other | Antioch · Contra Costa County | — | — |
| Integra Design Build | Integra Design Build | — | (510) 234 9830 | GC, remodel, ADU | El Cerrito · Contra Costa County | — | — |
| Integral Fire Protection INC | Arpad Sipos | — | (925) 206 9508 | Other | Pittsburg · Contra Costa County | — | — |
| Integrated Building Solutions INC | Eugene Gutkin | — | (925) 244 1900 | Electricians | San Ramon · Contra Costa County | — | — |
| Integrated Design Build Project Solutions | Mir Sulaiman Amini | — | (424) 353 9801 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Integrated Electrical Technologies LLC | Esso Bodjolle-Kapsa | — | (804) 869 2727 | Electricians | Concord · Contra Costa County | — | — |
| Integrit Construction INC | Earl John Boyce | — | (775) 762 6775 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Integrity Air Conditioning And Heating | Integrity Air Conditioning And Heating | — | (661) 902 8768 | HVAC | Antioch · Contra Costa County | — | — |
| Integrity First Construction | Waldrup Calvin | — | (510) 207 7479 | GC, remodel, ADU | El Cerrito · Contra Costa County | — | — |
| Integrity Roofing Systems | Integrity Roofing Systems | — | (925) 248-9000 | Other roofers | Pleasanton · Contra Costa County | — | — |