| 2 Minds Design Construction | Gonzalo Flores-Mayorga | — | (619) 721 7537 | GC, remodel, ADU | Escondido · San Diego County | — | — |
| 2-d Stage Lighting Electric INC | Tracy Lloyd Boen | info@2dstageelectric.com | (619) 327 8866 | Electricians | El Cajon · San Diego County | — | — |
| 20/20 Painting Company | George Kais Gilou | — | (619) 754 3680 | Windows, patio, painters | La Mesa · San Diego County | — | — |
| 2020 Universal | 2020 Universal | — | (760) 497 0212 | Windows, patio, painters | Vista · San Diego County | — | — |
| 21 Century Tile And Stone INC | Gustavo Ernesto Ortiz | — | (619) 748 0924 | Other | San Ysidro · San Diego County | — | — |
| 21 Degrees Construction | Martinez Hernandez Sergio | — | (760) 519 7414 | GC, remodel, ADU | Escondido · San Diego County | — | — |
| 211 Plumbing & Drains INC | Jose Alexis Alviter Arzate | — | (760) 557 9413 | Other | Oceanside · San Diego County | — | — |
| 21M Construction Co | Francisco Javier Oseguera | — | (619) 215 3335 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 21st Century Design | 21st Century Design | — | (619) 708 6725 | GC, remodel, ADU | Escondido · San Diego County | — | — |
| 21st Century Electric | Paul Harry Bussell | typesetit@att.net | (760) 809 8285 | Electricians | Encinitas · San Diego County | — | — |
| 21st Century Pool Maintenance | 21st Century Pool Maintenance | — | (619) 995 5105 | Pool | Santee · San Diego County | — | — |
| 24 / 7 Pro Construction INC | Zeena George Alsheikh | — | (619) 607 2507 | GC, remodel, ADU | Chula Vista · San Diego County | — | — |
| 24 / 7 Trucking INC | Kevin Darrell Gilliam | — | (619) 262 5171 | Other | San Diego · San Diego County | — | — |
| 24 Hour Bathtub Refinishers | Miguel Cano Lopez | — | (619) 990 9944 | Other | La Mesa · San Diego County | — | — |
| 24 Hour Plumbing And Leak Detection | Tuan Ba Pham | — | (619) 885 5960 | Other | San Diego · San Diego County | — | — |
| 24 Seven Tree Service | Garduno Jennifer | — | (760) 500 1393 | Tree | Vista · San Diego County | — | — |
| 24/7 Drain Rooter INC | James Norman Padgett | interested@domainmarket.com | (619) 303 3575 | HVAC | El Cajon · San Diego County | — | — |
| 24/7 Thuro-dry Flood Services | Ron Allen Barnes | thurodry1@gmail.com | (858) 270 5600 | Other | San Diego · San Diego County | — | — |
| 2nd Gen Plumbing INC | Lopez Ivan Fernandez | — | (619) 607 8855 | Other | San Diego · San Diego County | — | — |
| 3 | Farid Andres Ayoubzadeh-Reyes | — | (619) 879 4105 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 3 - D Enterprises Incorporated | Elihu Shahrokh | office@3d-nt.com | (858) 530 2202 | HVAC | San Diego · San Diego County | — | — |
| 3 Blind Mice Window Coverings INC | Scot Thomas Dietz | — | (858) 452 6100 | Other | San Diego · San Diego County | — | — |
| 3 C Framing | 3 C Framing | — | (760) 297 8532 | Other | San Marcos · San Diego County | — | — |
| 3 D Environmental INC | Drew Paul Castro | — | (619) 546 0105 | GC, remodel, ADU | Spring Valley · San Diego County | — | — |
| 3 Day Kitchen & Bath | Oved Yakir | info@3day-kitchenbath.com | (619) 558 6950 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 3 In 1 Bathtub And Kitchen Refinishing INC | Estrada Heriberto | — | (619) 575 9253 | Other | Chula Vista · San Diego County | — | — |
| 3 Lopez Brother's Construction Corp | Alejandro Gomez | — | (442) 245 9705 | GC, remodel, ADU | San Marcos · San Diego County | — | — |
| 3 M Electric | Mariano Amio Ocampo | shea@m-electric.com | (858) 357 1126 | Electricians | Escondido · San Diego County | — | — |
| 3 Peaks Construction LLC | Christopher Michael Rice | guy@infinitydesignbuild.com | (760) 212 5484 | GC, remodel, ADU | Carlsbad · San Diego County | — | — |
| 3-d Mobile Home Services INC | David Glenn Mckee | — | (760) 294 8209 | Other | Escondido · San Diego County | — | — |
| 3-points Design+build INC | Lisa Ann Molgren | hello@rfuenzalida.com | (310) 513 5453 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 321 Plumbing INC | Benito Estrada Chavez | — | (760) 215 9520 | Other | Escondido · San Diego County | — | — |
| 345 Concrete INC | Jose De Jesus Lopez Aguilar | — | (858) 401 0579 | Other | El Cajon · San Diego County | — | — |
| 360 Community Management | Geremy Alan Robenolt | — | (408) 559-1977 | GC, remodel, ADU | Santee · San Diego County | — | — |
| 360 Windows And Doors | Zachary Kayem Morrison | buildzoomsupport@blockrenovation.com | (619) 331 5246 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 365 Cleaning & Restoration | Leif Aaron Riley | jamil@symonsfp.com | (858) 652 9927 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 365 Plumbing INC | Fares Belanteur | — | (619) 724 8550 | Other | La Mesa · San Diego County | — | — |
| 3677 Columbia LLC | Ahmed Samih Eldahmy | — | (619) 313 1061 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 3:23 Metal Works INC | Christopher Robert Keys | support@metalworks.com | (442) 320 3237 | Other | Fallbrook · San Diego County | — | — |
| 3B Construction Company LLC | Brandon Gene Madeira Wilcox | guy@infinitydesignbuild.com | (760) 473 7125 | GC, remodel, ADU | Encinitas · San Diego County | — | — |