 Arnold is governed under Pennsylvania's third-class city code, with a mayor, treasurer, controller, and four council members elected at-large.Past mayors of Arnold have been M. Frank Horne (1939-1960), Alfred Colaianni (1960-1963), Willie DeMao (1963-2004), John Campbell (2004–2012), and Larry Milito (2012-2016).Karen Peconi-Biriccochi, a Democrat, took office in 2016.