The 38-year-old film star took the oath of office Tuesday in Scranton, Pa., the New York Daily News reported.
Sheriff John Szymanski, who snapped her ID photo, said Sorvino "would be a nice addition to the force. She's a very beautiful young lady."
However, he added, her badge "doesn't afford her any police powers. It's ceremonial."
Her dad, actor Paul Sorvino, received his deputy sheriff's badge in 1982, when he shot "That Championship Season" in Scranton. Szymanski has made Paul's son, Matthew, and Mira's husband, Chris Backus, deputy sheriffs as well.