| 10-4 Millwork | Roger De Castro Ferreira | — | (650) 863 2333 | Other | San Mateo · San Mateo County | — | — |
| 29 Dollar Plumbing | 29 Dollar Plumbing | — | (650) 999 9929 | Other | Burlingame · San Mateo County | — | — |
| 3 A Plumbing | 3 A Plumbing | — | (415) 404 1400 | Other | San Bruno · San Mateo County | — | — |
| 3 C I Systems Integration INC | Anne Cunningham Campbell | — | (415) 285 2629 | Other | Woodside · San Mateo County | — | — |
| 365 Plumbing & Rooter | 365 Plumbing & Rooter | — | (415) 368 3450 | Other | Daly City · San Mateo County | — | — |
| 3J Tile INC | Jose Roberto Juarez | — | (650) 399 6819 | Other | San Carlos · San Mateo County | — | — |
| 415 Drywall | 415 Drywall | — | (408) 722 2069 | Other | San Bruno · San Mateo County | — | — |
| 5 Star Building Maintenance LLC | Jace Deron Mcbee | — | (650) 533 4595 | Other | San Bruno · San Mateo County | — | — |
| A & D Welding INC | James Anthony Aveggio | web@adwelding.com | (650) 593 4040 | Other | San Carlos · San Mateo County | — | — |
| A & G Hardwood Flooring | A & G Hardwood Flooring | — | (650) 921 0998 | Other | San Mateo · San Mateo County | — | — |
| A & M Plumbing | A & M Plumbing | — | (408) 828 6446 | Other | Belmont · San Mateo County | — | — |
| A - 1 Hauling | A - 1 Hauling | — | (650) 270 5746 | Other | South San Francisco · San Mateo County | — | — |
| A 1 Budget Plumbing | A 1 Budget Plumbing | — | (650) 291 3743 | Other | Burlingame · San Mateo County | — | — |
| A B Heagney Metal Fabrication | A B Heagney Metal Fabrication | — | (650) 868 7448 | Other | Brisbane · San Mateo County | — | — |
| A B P Plumbing INC | Steve James Mc Creadie | — | (408) 757 6267 | Other | Belmont · San Mateo County | — | — |
| A B Plumbing | A B Plumbing | — | (415) 215 5821 | Other | San Bruno · San Mateo County | — | — |
| A C Earthworks | A C Earthworks | — | (650) 274 8244 | Other | Redwood City · San Mateo County | — | — |
| A G C | A G C | — | (415) 722 7711 | Other | Daly City · San Mateo County | — | — |
| A G Hansen Plumbing | A G Hansen Plumbing | — | (650) 323 4138 | Other | Menlo Park · San Mateo County | — | — |
| A G R Plumbing | A G R Plumbing | — | (650) 921 4956 | Other | San Mateo · San Mateo County | — | — |
| A Mettle Production | A Mettle Production | — | (650) 302 2520 | Other | Pacifica · San Mateo County | — | — |
| A Miracle Plumbing | A Miracle Plumbing | — | (415) 574 7216 | Other | San Bruno · San Mateo County | — | — |
| A R T Carpets & Vinyl | Michael Walter Boettcher | — | (650) 278 9103 | Other | Pacifica · San Mateo County | — | — |
| Aa Networks Corp | Wai Lung Lui | — | (650) 872 1998 | Other | Burlingame · San Mateo County | — | — |
| Abs Plastering INC | Barrera Santiago Ambrocio | — | (650) 245 3482 | Other | San Mateo · San Mateo County | — | — |
| Absolute Flooring | Betty Elizabeth Husari | — | (650) 661 8153 | Other | Half Moon Bay · San Mateo County | — | — |
| Access Door Solutions INC | Scott Shelton Nola Untiedt | — | (650) 766 0719 | Other | Daly City · San Mateo County | — | — |
| Access Soil Drilling INC | Jonathan Justin Fone | max@accesssoildrilling.com | (650) 808 2200 | Other | San Carlos · San Mateo County | — | — |
| Access/affordable Floor And Window Coverings | Access/affordable Floor And Window Coverings | — | (650) 591 3822 | Other | Belmont · San Mateo County | — | — |
| Acme Mechanical | Acme Mechanical | — | (650) 759 2990 | Other | San Mateo · San Mateo County | — | — |
| Adam O'neill Locksmith | Adam O'neill Locksmith | — | (415) 425 0996 | Other | South San Francisco · San Mateo County | — | — |
| Adaptive Networks LLC | Joel David Gutierrez | — | (650) 345 8000 | Other | Millbrae · San Mateo County | — | — |
| Adl Plumbing | Adl Plumbing | — | (713) 927-1993 | Other | South San Francisco · San Mateo County | — | — |
| Advance Systems And Design | Advance Systems And Design | — | (650) 363 8053 | Other | Redwood City · San Mateo County | — | — |
| Advanced Automatic Gates | Advanced Automatic Gates | — | (650) 594 4814 | Other | Belmont · San Mateo County | — | — |
| Advantage Plumbing Sf INC | Daniel Thomas Walker | — | (415) 342 8135 | Other | South San Francisco · San Mateo County | — | — |
| Afb Plumbing | Afb Plumbing | — | (650) 576 4549 | Other | Pacifica · San Mateo County | — | — |
| Affinitel Communications | Fabio Rogerio Penny | — | (415) 808 7200 | Other | Daly City · San Mateo County | — | — |
| Ags Signs | Ags Signs | — | (415) 840 4337 | Other | San Bruno · San Mateo County | — | — |
| Aguilar & Sons INC | Keith Edward Aguilar | — | (650) 344 1400 | Other | Burlingame · San Mateo County | — | — |