Police say Clemmens stuck his fingers down his throat and vomited on Easton police Captain Michael Vangelo and his daughter during an April 14 Phillies-Nationals game after his companion was ejected from the park.
Sentencing is set for July 30.
Assistant District Attorney Patrick Doyle says sentencing guidelines call for Clemmens to get probation. He says the Vangelo family is satisfied by the plea.
Clemmens' attorney was not immediately available following the hearing.