The following counties and library systems have reciprocal borrowing agreements with KCLS:
- Chelan County
- Clallam County
- Clark County, excluding Camas
- Douglas County, excluding Mansfield, Rock Island
- Everett Public Library
- Ferry County, excluding Kettle Falls
- Fort Vancouver Regional Library
- Grant County, excluding Hartline, Marlin, Wilson Creek
- Grays Harbor County, excluding Ocean Shores
- Island County
- Jefferson County Rural Library District
- Kitsap Regional Library
- Klickitat County
- Lewis County, excluding Mossy Rock, Napavine, Pe Ell, Vader
- Mason County
- Milton Public Library (annexed to Pierce County Library System)
- North Central Regional Library
- North Olympic Library System
- Okanogan County, excluding Conconully, Nespelem
- Pacific County
- Pierce County Library System, excluding Carbonado, Fircrest, Roy, Ruston
- Port Townsend Public Library
- Puyallup Public Library
- Skamania County
- Sno-Isle Regional Library
- Snohomish County, excluding Woodway
- Tacoma Public Library (residents must have a valid card from their "home" library before adding the reciprocal card from KCLS)
- Thurston County
- Timberland Regional Library
- Woodland in Cowlitz County
