| Wind And C Construction | Aum Windspirit | — | (707) 357 1472 | GC, remodel, ADU | Albion · Mendocino County | — | — |
| Winter Construction | Leonard William Ii Winter | — | (707) 462 1414 | GC, remodel, ADU | Ukiah · Mendocino County | — | — |
| Winzler Custom Framing | Winzler Custom Framing | — | (707) 318 3657 | Other | Ukiah · Mendocino County | — | — |
| Wipf General Engineering | Ernest Mark Wipf | — | (707) 462 8741 | Other | Ukiah · Mendocino County | — | — |
| Wood Joint Studio | Robert John Sanderson | — | (707) 961 5452 | Other | Fort Bragg · Mendocino County | — | — |
| Woodcycle | Alex Eugene Murray | — | (707) 462 0740 | Other | Ukiah · Mendocino County | — | — |
| Woodline Design INC | James Robert Hinkle | albert@woodlinedesign.com | (707) 841 0447 | Other | Willits · Mendocino County | — | — |
| World Restoration Services INC | Devereaux Nathan Cash | — | (707) 354 2522 | GC, remodel, ADU | Ukiah · Mendocino County | — | — |
| Wyatt Silva | Wyatt Silva | info@wyattsilva.com | (707) 272 9746 | Other | Laytonville · Mendocino County | — | — |
| Wylatti Enterprises LLC DBA Geo Aggregates | Brian Keith Hurt | — | (707) 964 4033 | Other | Fort Bragg · Mendocino County | — | — |
| Wylatti Resource Management INC | Brian Keith Hurt | — | (707) 983 8135 | Tree | Covelo · Mendocino County | — | — |
| Young Construction | Joel Cameron Young | — | (707) 376 5774 | GC, remodel, ADU | Ukiah · Mendocino County | — | — |
| Zack Szychowski Construction | Zack Williams Szychowski | — | (707) 513 8025 | GC, remodel, ADU | Mendocino · Mendocino County | — | — |
| Zarraga Construction | Jorge Alberto Zarraga Barron | — | (707) 621 2609 | GC, remodel, ADU | Fort Bragg · Mendocino County | — | — |