The 30-year-old deputy with the Orange County Sheriff's Department could face charges including assault under the color of authority and sexual activity between a peace officer and inmate, according to a department statement.
An investigation began Aug. 8 when staff at Theo Lacy jail intercepted unspecified communication that described the alleged misconduct, the statement said.
The deputy is suspected of establishing an inappropriate relationship with two female inmates starting in May.
"He is alleged to have sexually assaulted the female inmates separately on multiple occasions by touching them in a sexual manner over their clothes and showing them pornographic videos while in their housing locations," the department statement said.
The case will be forwarded to the Orange County District Attorney's Office for prosecution.
The deputy has been placed on administrative leave during the investigation.
Orange Supervisor Katrina Foley released a statement, calling the alleged assaults "an abuse of power."
"Such egregious dereliction of duty and abuse of power over vulnerable women must not be tolerated. I'm proud of the jail staff who discovered and quickly reported the abuse," said Supervisor Foley. "I respect the swift action taken by our Orange County Sheriff's Department to remove this predator within 24 hours of notice. We cannot allow bad actors to betray their oath to protect and serve."
The Associated Press contributed to this report.