Forty-year-old Rahim Montgomery is accused of sexually assaulting a minor approximately five years ago.
Investigators said the crime was reported in July 2020.
He was arrested on Friday by the Philadelphia Police Department's Internal Affairs Division.
Montgomery is a 20-year veteran of the department, most recently assigned to the 9th district.
The Philadelphia District Attorney's Office has charged Montgomery with one count of Unlawful Contact with a Minor to Commit Indecent Assault/Indecent Exposure, one count of Indecent Assault, one count of Indecent Exposure, and Corruption of Minors.
Philadelphia Police Commissioner Danielle Outlaw has suspended Montgomery for 30 days with the intent to dismiss at the end of the 30 days.