| The Plumberman | The Plumberman | — | (707) 442 8345 | Other | Eureka · Humboldt County | — | — |
| The Stove Doctors | The Stove Doctors | — | (707) 601 8369 | Other | Mc Kinleyville · Humboldt County | — | — |
| Thomas Home Center INC | Thomas Carl Rector | — | (707) 839 3222 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Thomas R Bess INC | Thomas Roy Bess | — | (707) 499 0304 | Other | Carlotta · Humboldt County | — | — |
| Thompson Construction | Ryan Steven Thompson | tthompson1024@gmail.com | (707) 502 7289 | GC, remodel, ADU | Fortuna · Humboldt County | — | — |
| Thompson Construction | Jeffrey Durland Thompson | tthompson1024@gmail.com | (707) 502 4047 | GC, remodel, ADU | Fortuna · Humboldt County | — | — |
| Thomsen Construction | Cory Michael Thomsen | — | (707) 851 3030 | GC, remodel, ADU | Hydesville · Humboldt County | — | — |
| Thrap & Company | Tyler Alan Thrap | — | (707) 599 6123 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Tile By Bavin | Tile By Bavin | — | (707) 496 2649 | Other | Arcata · Humboldt County | — | — |
| Tile Unlimited | Tile Unlimited | — | (707) 499 4345 | Other | Kneeland · Humboldt County | — | — |
| Tim Arnold | Tim Arnold | instructor@timarnold.com | (707) 497 7865 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Tim Davy Construction | Timothy James Davy | — | (707) 496 3888 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Tim Mansfield Construction | Timothy Abercrombie Mansfield | — | (707) 498 9099 | GC, remodel, ADU | Arcata · Humboldt County | — | — |
| Tim Martin Construction | Timothy Sean Martin | — | (650) 773 9051 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Tim's Plumbing | Tim's Plumbing | — | (707) 499 1266 | Other | Eureka · Humboldt County | — | — |
| Timber & Tile Construction LLC DBA Timber Construction | Brad Lee Rajor Harris | — | (707) 267 7442 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Timmerman Painting | Timmerman Painting | — | (707) 498 3907 | Windows, patio, painters | Hydesville · Humboldt County | — | — |
| Toby Mays Construction | Toby Lee Roy Mays | — | (707) 839 5770 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Toland Construction | Jeff Boyd Toland | — | (707) 498 5556 | Other | Eureka · Humboldt County | — | — |
| Tomasini Tile | Tomasini Tile | — | (707) 496 2025 | Other | Fortuna · Humboldt County | — | — |
| Tompkins Construction | Tommy Lee Tompkins | — | (707) 499 0397 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Tony Karlich | Tony Karlich | — | (707) 443 2903 | Electricians | Eureka · Humboldt County | — | — |
| Travis Carmesin | Travis Carmesin | — | (707) 496 1637 | Other | Mc Kinleyville · Humboldt County | — | — |
| Tree Tactics | Tree Tactics | — | (707) 616 2929 | Tree | Fortuna · Humboldt County | — | — |
| Tree Ventures Inc. | Tree Ventures Inc. | office@treeventuresca.net | (707) 407-4077 | Tree | Humboldt · Humboldt County | — | — |
| Triad Contracting And Engineering | Jordan Mason Zizza | — | (707) 444 8007 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Trinidad Electric Incorporated | Walter Grant Lay | — | (707) 826 1407 | Electricians | Trinidad · Humboldt County | — | — |
| Trinidad Electrical | Trinidad Electrical | — | (707) 441-1231 | Electricians | Arcata · Humboldt County | — | — |
| Trinity River Electric INC | David Paul Lang - Gunn | — | (530) 629 6119 | Electricians | Willow Creek · Humboldt County | — | — |
| Triple Junction Landscaping | Nolan Robert Marshall | — | (559) 730 1837 | Windows, patio, painters | Arcata · Humboldt County | — | — |
| Troy M Combs DBA Fine Lines Painting | Fine Lines Painting | — | (707) 442 6959 | Windows, patio, painters | Eureka · Humboldt County | — | — |
| Truby Plumbing | Truby Plumbing | — | (707) 845 7618 | Other | Fortuna · Humboldt County | — | — |
| Tugboat Charlie's Construction Company | Carlos Adam Hernandez | — | (707) 267 0997 | GC, remodel, ADU | Fortuna · Humboldt County | — | — |
| Tyler Lewis | Tyler Lewis | — | (707) 223 3937 | Other | Garberville · Humboldt County | — | — |
| Ulrich Electric | Steven Alexander Ulrich | — | (707) 601 1414 | Electricians | Eureka · Humboldt County | — | — |
| Ultimate Building Solutions INC | Niels Christian Holgersen | — | (707) 496 6109 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| United Building | United Building | — | (707) 442 4638 | GC, remodel, ADU | Fields Landing · Humboldt County | — | — |
| United Plumbing & Mechanical | United Plumbing & Mechanical | — | (707) 499 4808 | Other | Fortuna · Humboldt County | — | — |
| Upgrade Painting Company | Steven Michael Toler | — | (707) 496 1469 | Windows, patio, painters | Eureka · Humboldt County | — | — |
| Van Duzen Construction | Steven J Mendonca | — | (707) 777 3508 | GC, remodel, ADU | Hydesville · Humboldt County | — | — |