| William Edward Latimer Electric | Marguerite Teresa Lethridge | — | (510) 305 8384 | Electricians | Oakland · Alameda County | — | — |
| William Jay Montgomery | William Jay Montgomery | — | (510) 794 9098 | Electricians | Newark · Alameda County | — | — |
| William Markus Electric | William Kenneth Ii Markus | — | (510) 372 6932 | Electricians | Oakland · Alameda County | — | — |
| William Roy Duterte | William Roy Duterte | — | (925) 876 9423 | GC, remodel, ADU | Livermore · Alameda County | — | — |
| William Terrence Plunkett | William Terrence Plunkett | — | (510) 461 1232 | GC, remodel, ADU | San Leandro · Alameda County | — | — |
| William Wai Wong | William Wai Wong | — | (510) 847 1199 | GC, remodel, ADU | San Leandro · Alameda County | — | — |
| Williams Electric | Geoffrey Allen Williams | info@williams-electric.com | (510) 339 5601 | Electricians | Oakland · Alameda County | — | — |
| Williams Professional Painting | Williams Professional Painting | — | (510) 677 2676 | Windows, patio, painters | Oakland · Alameda County | — | — |
| Williams Roofing | Steven Gene Williams | williamsadvancedroofing1@gmail.com | (510) 623 1424 | Other roofers | Fremont · Alameda County | — | — |
| Williams Underground Construction INC | Joshua Derek Williams | — | (925) 837 6766 | Other | Oakland · Alameda County | — | — |
| Willow Creek Construction INC | Blaine Mervin Munsch | info@willowcreekconstruction.com | (510) 714 9398 | GC, remodel, ADU | Pleasanton · Alameda County | — | — |
| Willy's Painting INC | Miguel Angel Sanchez-Olvera | — | (510) 355 5169 | Windows, patio, painters | Oakland · Alameda County | — | — |
| Wilmar's Painting | Wilmar S Gonzalez Velasquez | — | (510) 927 7886 | Windows, patio, painters | Oakland · Alameda County | — | — |
| Wilson Construction | Wilson Weiqiu Qi | — | (510) 882 4150 | GC, remodel, ADU | Castro Valley · Alameda County | — | — |
| Wilson Mechanical | Wilson Mechanical | — | (415) 568 1587 | HVAC | San Leandro · Alameda County | — | — |
| Wilson Young | Wilson Young | — | (510) 708 0114 | GC, remodel, ADU | Castro Valley · Alameda County | — | — |
| Wilton Construction | Joe Brian Wilton | — | (510) 917 1484 | GC, remodel, ADU | Alameda · Alameda County | — | — |
| Wimbish Construction | James Damon Wimbish | — | (510) 502 5218 | GC, remodel, ADU | Hayward · Alameda County | — | — |
| Win Power Construction And Electric Corporation | Chun Sing Yip | — | (510) 282 2882 | Electricians | San Leandro · Alameda County | — | — |
| Wind Construction | John August Wind | — | (650) 544 8660 | GC, remodel, ADU | Hayward · Alameda County | — | — |
| Wind River Services INC | Dale Craig Skinner | — | (925) 997 8123 | GC, remodel, ADU | Dublin · Alameda County | — | — |
| Windemere Electric | Mark Cun To | — | (510) 882 0651 | Electricians | Fremont · Alameda County | — | — |
| Window & Door Solutions INC DBA K G Woodworking | Kenneth Anthony Gillett | — | (510) 415 1944 | Other | Hayward · Alameda County | — | — |
| Window Decor | Window Decor | — | (510) 213 1043 | Other | Alameda · Alameda County | — | — |
| Windypeak Landscaping INC | Cesar Gudiel Martin Cruz | sales@windypeaklandscaping.com | (510) 253 5557 | Windows, patio, painters | Oakland · Alameda County | — | — |
| Wing On Construction INC | Yuejun Chen | jim138@msn.com | (510) 786 8838 | GC, remodel, ADU | San Leandro · Alameda County | — | — |
| Wing's Roofing INC | Wing Jik Chea | — | (408) 506 0510 | Other roofers | Castro Valley · Alameda County | — | — |
| Wingate Building | Wingate Building | — | (510) 290 1289 | GC, remodel, ADU | Oakland · Alameda County | — | — |
| Winko General Construction | Ma Chi Wing | — | (415) 335 8460 | GC, remodel, ADU | San Lorenzo · Alameda County | — | — |
| Winston's Plumbing | Winston's Plumbing | — | (510) 652 8014 | Other | Oakland · Alameda County | — | — |
| Winters Construction | Douglas Michael Winters | — | (925) 989 4327 | GC, remodel, ADU | Pleasanton · Alameda County | — | — |
| Wire Fitter Tech | Wire Fitter Tech | — | (510) 738 1978 | Other | Union City · Alameda County | — | — |
| Wire Mile Corp DBA Budget Blinds Of San Leandro | Lea Renata Taylor | — | (510) 370 3360 | Other | San Leandro · Alameda County | — | — |
| Wired Right Electric LLC | Joseph Dee | — | (925) 980 9763 | Electricians | Livermore · Alameda County | — | — |
| Wirsig Concrete Structures | Wirsig Concrete Structures | — | (510) 385 0283 | Other | Berkeley · Alameda County | — | — |
| Wishnev Computer & A/v Consulting | Jonathan Micah Wishnev | — | (510) 333 1576 | Other | Oakland · Alameda County | — | — |
| Wj&y Construction INC | Weiping Yin | — | (415) 867 9266 | GC, remodel, ADU | Hayward · Alameda County | — | — |
| Wm A Barron Co | Bruce William Barron | — | (925) 556 1980 | Other | Dublin · Alameda County | — | — |
| Wma Landscape Construction INC | William Morris Ayers | — | (925) 344 5006 | GC, remodel, ADU | Livermore · Alameda County | — | — |
| Wolfe INC | Spencer Cameron Wolfe | — | (510) 289 1344 | GC, remodel, ADU | Oakland · Alameda County | — | — |