William Rodriguez, 33, was arrested Tuesday on two felony counts of forcible rape, and is expected to be arraigned Thursday, the Los Angeles County district attorney's office said.
Rodriguez, a 10-year veteran of the Los Angeles Police Department, initially was accused of one assault -- allegedly raping a female acquaintance at his home on Nov. 1, prosecutors say.
That matched him with evidence in an unsolved sexual assault of a female in 2015, the district attorney's office said.
Rodriguez was off-duty during both assaults, according to the district attorney's office.
He was most recently working for the LAPD's Valley Traffic Division, which investigates crashes and traffic-related crimes in parts of northwestern Los Angeles.