| Jtb Artificial Turf Landscape | Justin Lee Glakeler | — | (530) 258 6277 | Windows, patio, painters | Lakeport · Lake County | — | — |
| Juarez & Manjarres Painting | Flores Samuel Juarez | — | (707) 227 5675 | Windows, patio, painters | Clearlake · Lake County | — | — |
| Justin's Roofing | Justin Robert Ross | — | (707) 295 5543 | Other roofers | Clearlake · Lake County | — | — |
| K & R Tree Specialists INC | Kyle Robert Shields | — | (707) 355 1865 | Tree | Clearlake · Lake County | — | — |
| Kapono Meyer Concrete INC | Kapono Alii Meyer | — | (707) 396 1706 | Other | Middletown · Lake County | — | — |
| Keith Hooten Construction | Keith Byron Hooten | — | (707) 995 3001 | GC, remodel, ADU | Clearlake · Lake County | — | — |
| Kimble's Construction | Ryan Charles Kimble | kimbleconstruction@att.net | (707) 972 8691 | GC, remodel, ADU | Clearlake · Lake County | — | — |
| Kit R Larsen | Kit R Larsen | — | (707) 694 8071 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Kl Smith Construction Company | Kimberly Louann Smith | — | (707) 484 1587 | Other | Middletown · Lake County | — | — |
| Klatt Construction/design | Gregory Mathew Klatt | — | (707) 591 5577 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Kysely Construction | Brian Kenneth Kysely | — | (707) 245 7012 | GC, remodel, ADU | Finley · Lake County | — | — |
| L S P Construction | Louis Sid Percaccio | — | (707) 972 7489 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Lake Arrowhead Security Suite #o1-270 28200 California Ca-189 #03-0170 | Lake Arrowhead Security Suite #o1-270 28200 California Ca-189 #03-0170 | — | (909) 337-2023 | Alarm and generators | Lake Arrowhead · Lake County | — | — |
| Lake Builders INC | Steven Lee Mc Sween | — | (707) 987 2265 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Lake County Drywall | Lake County Drywall | — | (707) 263 5066 | Other | Lakeport · Lake County | — | — |
| Lake County Fence | Lake County Fence | — | (707) 413 8940 | Other | Lakeport · Lake County | — | — |
| Lake County Landscaping | Lake County Landscaping | — | (707) 245 1311 | Windows, patio, painters | Kelseyville · Lake County | — | — |
| Lake County Pump LLC | Matthew Edward Thibodeaux | — | (707) 972 7808 | Other | Lakeport · Lake County | — | — |
| Lake County Pumpers LLC | Jonathan Thomas Philpot | lakecountypumpers@gmail.com | (707) 672 9023 | Other | Lower Lake · Lake County | — | — |
| Lake County Tree Service | Jose Emilio Juarez | — | (707) 279 9501 | Tree | Kelseyville · Lake County | — | — |
| Lake Elsinore Pest Control Pros | Lake Elsinore Pest Control Pros | info@lakeelsinorecapestcontrol.com | (951) 592-2033 | Pest, tile roofs | Lake Elsinore · Lake County | — | — |
| Lake Forest Electric | Lake Forest Electric | — | (949) 519-1321 | Electricians | Lake Forest · Lake County | — | — |
| Lake Forest Pest Control | Lake Forest Pest Control | — | (949) 329-2838 | Pest, tile roofs | Lake Forest · Lake County | — | — |
| Lake Forest Roofing | Lake Forest Roofing | — | (949) 478-5325 | Other roofers | Lake Forest · Lake County | — | — |
| Lake HVAC | Lake HVAC | — | (781) 438-8814 | HVAC | Lake · Lake County | — | — |
| Lake Tree Service | Lake Tree Service | laketreeservice@gmail.com | (269) 416-0625 | Tree | Lake · Lake County | — | — |
| Lakeport Glass & Door | Lakeport Glass & Door | — | (707) 263 1933 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Lakeshore Plumbing | Lakeshore Plumbing | — | (707) 533 3226 | Other | Lucerne · Lake County | — | — |
| Landrum Construction | Christopher Lee Landrum | — | (707) 263 7522 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Lang Contracting | Lang Contracting | — | (760) 634-0830 | GC, remodel, ADU | Cardiff · Lake County | — | — |
| Lcv Handyman | Lcv Handyman | corey@lcvhandyman.com | (760) 405-1774 | Electricians | Carlsbad · Lake County | — | — |
| Lee Ericson Const | Lee Ericson Const | — | (831) 345 7355 | GC, remodel, ADU | Hidden Valley Lake · Lake County | — | — |
| Lescher Construction | Shawn Christopher Lescher | — | (707) 495 9974 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Lexicon Construction | Hofmarcher Werner | — | (707) 321 5908 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Light Ray Electric | Ross Robert Eppler | — | (707) 719 0509 | Electricians | Lakeport · Lake County | — | — |
| Lovings Fireplace Service | Ryan James Loving | — | (707) 263 1900 | Other | Upper Lake · Lake County | — | — |
| Lowell Drywall | Lowell Drywall | — | (707) 621 3511 | Other | Nice · Lake County | — | — |
| Lucas Hauptmann Woodworking | Lucas Hauptmann Woodworking | — | (707) 337 5647 | Other | Middletown · Lake County | — | — |
| Lucchesi Specialties | Jedaiah Dalziel Black | — | (628) 999 5808 | GC, remodel, ADU | Finley · Lake County | — | — |
| Lucerne Roofing & Supply INC | John Michael Hagan | — | (707) 263 4200 | Tile distributors | Lakeport · Lake County | — | — |