In 1916, Westerville became the first village in Ohio to adopt a council-manager form of government, in which a city council makes policy but the town's administrative and many of its executive governmental functions are vested in an appointed, professional manager. Westerville retains the council-manager system to the present. The city elects seven council members at large for four-year terms; the council selects from among its own a member to serve as mayor, vice mayor, chair, and vice chair. Under the City Charter, the mayor is only "the ceremonial head of the government" of the city. The council additionally selects the city manager, who serves indefinitely. In 2007, David Collinsworth replaced David Lindimore as city manager after the latter's tenure of twenty-two years.
In 1995 the city annexed 941 non-dry acres of land to its north, which included several alcohol-selling businesses. Subsequently, voters have approved alcohol sales in old Westerville at a number of establishments through site-specific local options. In 2006 Michael's Pizza served the first beer in Uptown Westerville in over 70 years.
According to the United States Census Bureau, the city has a total area of 12.61 square miles (32.66 km2), of which, 12.47 square miles (32.30 km2) is land and 0.14 square miles (0.36 km2) is water.
According to a 2007 estimate, the median income for a household in the city was $73,540, and the median income for a family was $90,430. Males had a median income of $55,053 versus $36,510 for females. The per capita income for the city was $29,401. About 2.5% of families and 3.5% of the population were below the poverty line, including 3.5% of those under age 18 and 5.0% of those age 65 or over.