| Lemke Construction | Scott Allen Lemke | — | (707) 672 2938 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Leonardo Builders Incorporated | Shaun Anthony Leonardo | — | (707) 496 3239 | GC, remodel, ADU | Ferndale · Humboldt County | — | — |
| Light Construction | Matthew David Light | — | (707) 499 3653 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Lindquist Landscapes | Lindquist Landscapes | — | (707) 496 5532 | Windows, patio, painters | Trinidad · Humboldt County | — | — |
| Lindstrom Construction INC | Antonio Deleon | — | (707) 719 2466 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Little River Construction | John Michael Kinn | — | (707) 677 0351 | GC, remodel, ADU | Trinidad · Humboldt County | — | — |
| Live Oak Builders | Live Oak Builders | — | (707) 267 5233 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Living Earth Landscapes | Living Earth Landscapes | lel@livingearthlandscapes.com | (707) 822 7663 | Windows, patio, painters | Mc Kinleyville · Humboldt County | — | — |
| Lizard's Plumbing | Lizard's Plumbing | anapbm@gmail.com | (707) 498 7796 | Other | Arcata · Humboldt County | — | — |
| Ljg Builders LLC | Larry James Jr Gonzales | l.gonzales@ljgbuilders.com | (707) 497 7012 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Lodes Plumbing | Lodes Plumbing | — | (707) 616 0491 | Other | Eureka · Humboldt County | — | — |
| Logan's General Construction | Logan Michael Floyd | — | (707) 834 7466 | GC, remodel, ADU | Fortuna · Humboldt County | — | — |
| Long Branch Construction | James Byron Puntonio | — | (707) 498 5630 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Lost Coast Construction Services | Cyrus Orion Farrell | — | (707) 798 0753 | GC, remodel, ADU | Rio Dell · Humboldt County | — | — |
| Lost Coast Tree And Habitat | Lost Coast Tree And Habitat | — | (707) 496 9607 | Tree | Whitethorn · Humboldt County | — | — |
| Love Construction | Wade Willson Love | — | (707) 599 1717 | GC, remodel, ADU | Arcata · Humboldt County | — | — |
| Luke Bongio Construction | Lucas Robin Bongio | — | (707) 499 7834 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Lusk Landscapes | Lusk Landscapes | lusklandscapes@gmail.com | (707) 839 9135 | Windows, patio, painters | Willow Creek · Humboldt County | — | — |
| Luster Construction Company INC | Brice Eugene Luster | — | (707) 601 1650 | GC, remodel, ADU | Hydesville · Humboldt County | — | — |
| M C Electric | Marci Lynn Colburn | — | (707) 498 1421 | Electricians | Willow Creek · Humboldt County | — | — |
| M D John Construction | Matthew David John | — | (707) 570 7313 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| M.d.l. Construction | Mitchell David Lawrence | — | (707) 834 3013 | GC, remodel, ADU | Orick · Humboldt County | — | — |
| M.e. Construction Services INC | Luis Miguel Esparza Zermeno | m.econstruction16@gmail.com | (707) 601 4444 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Mac's Refrigeration Service | David Lee Mc Donald | — | (707) 442 8712 | HVAC | Eureka · Humboldt County | — | — |
| Mad River Builders | Ronnie Joe Franklin | — | (707) 834 4509 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Mad River Communication Services | Jude Anson Ehrlich | — | (707) 834 4553 | Other | Mc Kinleyville · Humboldt County | — | — |
| Mad River Construction | Daniel Richard Jones | — | (707) 496 5940 | GC, remodel, ADU | Arcata · Humboldt County | — | — |
| Mana Landscapes | Mana Landscapes | info@manalandscapes.com | (707) 572 0496 | Windows, patio, painters | Hydesville · Humboldt County | — | — |
| Mapleservice Incorporated | Roger Lee Maples | — | (707) 445 9671 | HVAC | Eureka · Humboldt County | — | — |
| Marc Malfatti Electric | Marc Richard Malfatti | — | (707) 498 6982 | Electricians | Eureka · Humboldt County | — | — |
| Marchi Construction | Raymond Floyd Marchi | — | (707) 499 5726 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Marcus Daniels | Marcus Daniels | — | (707) 834 3893 | GC, remodel, ADU | Ferndale · Humboldt County | — | — |
| Marenghi Construction Company | Marenghi Joseph | — | (707) 223 2738 | GC, remodel, ADU | Shelter Cove · Humboldt County | — | — |
| Mark Hilovsky | Mark Hilovsky | — | (707) 499 5248 | Electricians | Garberville · Humboldt County | — | — |
| Mark Huntington | Mark Huntington | — | (707) 923 3917 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Mark L Raymond Construction & Development Company | Mark Lawrence Raymond | — | (707) 499 5961 | GC, remodel, ADU | Arcata · Humboldt County | — | — |
| Mark Sloper Construction | Mark Robert Sloper | — | (707) 498 4303 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Mark Vellis Construction | Mark Lewis Vellis | — | (707) 499 6845 | GC, remodel, ADU | Fortuna · Humboldt County | — | — |
| Martin Bros Const | Kolton James Martin | — | (707) 502 7095 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Martin Construction | Keith Jon Martin | — | (707) 616 1161 | GC, remodel, ADU | Eureka · Humboldt County | — | — |