Authorities said the victim went to the recruiter's office for a practice written test March 9.
Officials say 40-year-old Van Van Tran got the woman into his car, telling her they were going to a library to get study aids for the exam.
Instead, investigators said he allegedly drove the unidentified woman to an area near her home and sexually assaulted her. The woman immediately contacted police and an investigation began.
The U.S. Navy is also conducting its own investigation into the incident.
The Los Angeles County District Attorney's Office said Tran was taken into custody Wednesday by El Monte police. He was charged Aug. 12 with one count of sexual penetration by a foreign object.
If convicted, Tran faces up to eight years in prison. He's being held on $100,000 bail. He is set to be arraigned in Pomona Friday.
The Associated Press contributed to this report.