| Atlas Kinetics INC | Philip Randolf Jr Horn | — | (619) 831 1606 | Other | Escondido · San Diego County | — | — |
| Atlas Legacy General Construction | Americo Michael Hernandez | — | (619) 455 8112 | GC, remodel, ADU | El Cajon · San Diego County | — | — |
| Atlas Mechanical INC | Shekhter Semyon | — | (858) 554 0700 | HVAC | San Diego · San Diego County | — | — |
| Atlas Roofing | Atlas Roofing | — | (866) 450-3981 | Other roofers | San Diego · San Diego County | — | — |
| Atlas Roofing San Diego | Santana Enrique Segura | mcgrawr04@gmail.com | (619) 990 2308 | Other roofers | San Diego · San Diego County | — | — |
| Atlas Tile Company INC | Jaime Jr Gonzalez | — | (619) 245 1568 | Other | National City · San Diego County | — | — |
| Atlas West Construction Corp | Frank Preclaro Gosteli | — | (619) 663 5316 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| Atmos Design Build | Atmos Design Build | — | (760) 421 1774 | GC, remodel, ADU | Ramona · San Diego County | — | — |
| Atmosphere Construction And Design | Magallon Katherine | — | (619) 934 4501 | GC, remodel, ADU | Escondido · San Diego County | — | — |
| Atolvo Enterprise | Atolvo Enterprise | — | (619) 573 6860 | GC, remodel, ADU | Escondido · San Diego County | — | — |
| Atom Modular | Atom Modular | — | (619) 200 9580 | GC, remodel, ADU | Bonita · San Diego County | — | — |
| Atomic Blast INC | Mark Donald Geelan | — | (619) 787 1422 | Other | San Diego · San Diego County | — | — |
| Atomic Investments INC | Leonard Edward Teyssier | info@atomic-inc.com | (619) 234 7966 | GC, remodel, ADU | National City · San Diego County | — | — |
| Atr Mechanical Solutions | Juan Enrique Jr San Vicente | service@atrmechanicalsolutions.com | (619) 971 8155 | HVAC | Poway · San Diego County | — | — |
| Atrax Construction | Daniel Fredrick Hare | — | (916) 218 9181 | GC, remodel, ADU | El Cajon · San Diego County | — | — |
| Ats Electric | Albert Thomas Sejut | eddie.haro@electricare.com | (760) 505 2233 | Electricians | Oceanside · San Diego County | — | — |
| Ats Heating And Air Corp | Arthur Aguilar | mn@tritonair.net | (619) 375 9185 | HVAC | San Diego · San Diego County | — | — |
| Atta Plumbing INC | James Macdonald Attaway | — | (619) 210 3877 | Other | Chula Vista · San Diego County | — | — |
| Attention Getters Design INC | Calvin Edward Kennedy | — | (619) 441 8901 | Other | El Cajon · San Diego County | — | — |
| Attested Carpets And Flooring | Attested Carpets And Flooring | — | (760) 644 9493 | Other | Escondido · San Diego County | — | — |
| Attic Advisor | Malka Maimon | — | (949) 316 8844 | GC, remodel, ADU | Carlsbad · San Diego County | — | — |
| Attic Heroes INC | Nicholas Teodor Kildiszew | office@theatticheroes.com | (619) 777 7021 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| Attic Projects LLC | Einav Eido | office@atticprojects-la.com | (619) 880 5089 | Electricians | San Diego · San Diego County | — | — |
| Atticguard Construction | Qin Ji | — | (760) 975 9506 | GC, remodel, ADU | Escondido · San Diego County | — | — |
| Atticshield | Elliott Shlomo Hadida | info@atticshield.com | (858) 402 0066 | GC, remodel, ADU | Escondido · San Diego County | — | — |
| Atzel Electric Solutions INC | Solano Fernando Zapata | eddie.haro@electricare.com | (760) 402 1046 | Electricians | Escondido · San Diego County | — | — |
| Audio Impact INC | Ryan Raul Lipkovicius | sales@audioimpact.com | (858) 271 4154 | Electricians | San Diego · San Diego County | — | — |
| Audio Innovations | Audio Innovations | — | (619) 322 3835 | Electricians | Santee · San Diego County | — | — |
| Audio Video Installs | Audio Video Installs | — | (619) 884 0167 | Other | Santee · San Diego County | — | — |
| Audio Video San Diego | David Arthur Troisi | — | (760) 575 4819 | Other | Carlsbad · San Diego County | — | — |
| Audio Video Solutions | Audio Video Solutions | — | (619) 813 0519 | Other | Imperial Beach · San Diego County | — | — |
| Audio Video Strategy Group INC | Dennis Gene Pappenfus | — | (619) 436 1828 | Other | San Diego · San Diego County | — | — |
| Audio/video Consulting | John Gill Walker | info@audiovideoconsulting.de | (760) 445 5181 | Other | San Diego · San Diego County | — | — |
| Audiothority INC | Chad Michael Colvin | info@audiothority.com | (760) 644 0408 | Electricians | Escondido · San Diego County | — | — |
| Audit Masters & Communications INC | Stephen Powers Quinones | — | (760) 535 1091 | Other | Vista · San Diego County | — | — |
| Audrey Fence Co | Jose Armando Campillo | contact@sansoxygen.com | (619) 787 1000 | Other | National City · San Diego County | — | — |
| Augie's Plumbing | Augie's Plumbing | — | (619) 944 8402 | Other | San Diego · San Diego County | — | — |
| Augustus Moretti | Augustus Moretti | — | (760) 681 8948 | Other | Warner Springs · San Diego County | — | — |
| Aura Design Build LLC | Dhurgham Sabah Aljuboori | info@auradesignbuild.net | (858) 833 6743 | Electricians | San Diego · San Diego County | — | — |
| Auscal Construction | Ryan Joshua Hall | ryan@auscalconstruction.com | (619) 799 8152 | GC, remodel, ADU | Chula Vista · San Diego County | — | — |