As in 34 of Washington States' 39 counties, the Adams County Board of County Commissioners is the county's legislative authority. The Commissioners serve as the chief administrators for many important county operations. Each of the three commissioners is elected to a four year term.

The Board levies all County taxes and appropriates all funds for expenditure through the budget process. It sets land use policy in the unincorporated areas and hears appeals to land use decisions. It enacts ordinances which has the force of law in the County. It appoints members of citizen advisory panels, hearing examiners, and members of the Board of Equalization. It approves all contract and grant agreements. Elections are staggered so that no more than two commissioners stand for election in any single year.