Shauna Bishop, 44, a five-year veteran of the Sacramento County Sheriff, went to the police in Folsom on Thursday. She was released after her arrest - but is scheduled to appear in court next week and faces five felony counts, the Sacramento Bee reported.
Investigators began to monitor Bishop in May and the police later issued an arrest warrant against her.
Bishop has been on paid leave since the beginning of the investigation.
The alleged sexual acts occurred while she was not on duty, the authorities said.
It was not clear if Bishop had a lawyer.