Mercer Island has a
council–manager government, in which the elected, seven-member city council selects a
mayor from among its members. The councilmembers are elected
at-large to four-year terms, while the mayor serves a two-year term. The
city manager is the
chief executive of the city government and is hired by the city council. David Rosenbaum has served as mayor since 2026; the city manager has been Jessi Bon since 2020. Mercer Island's temporary
city hall is in the northeast part of the city in an
office park. It replaced the normal city hall, which closed in April 2023 after
asbestos was discovered in the
heating, ventilation, and air conditioning system. A new city hall was planned to be built along with a public safety building for the
police department on an adjacent property. In November 2025, Proposition No. 1—which would float approximately $103 million in bonds to fund a new building—did not receive the majority required to pass. The city's
fire department was disbanded in 2024 and replaced by contracted service from
Eastside Fire and Rescue, which provides
fire protection for several Eastside cities. The fire department's two
fire stations were retained along with the
firefighters. Mercer Island has its own police department with one
police station. The city government provides
tap water that is delivered by
Seattle Public Utilities and stored in two
reservoirs that can each hold of water.
Sewage treatment is provided by the King County government through a contract with the Mercer Island government. The Public Works Department operates an office facility, street maintenance facility, and city shop from a building south of the City Hall. In February 2021, a 6–1 majority of the Mercer Island City Council passed an ordinance prohibiting outdoor camping on public property, mainly to restrict
homeless and unhoused people from overnight stays. The ordinance was criticized by the
American Civil Liberties Union of Washington and other public advocates for the homeless. At the federal level, Mercer Island is located in the
9th congressional district, which includes some of southern King County as well as parts of Seattle and Bellevue. The city is part of the
41st legislative district at the state level, which elects one senator and two representatives. The district includes southern Bellevue,
Newcastle, and part of
Sammamish. The
King County Council's 6th district encompasses Mercer Island, Bellevue,
Redmond, and other Eastside communities. ==Parks and recreation==