Michael Brandon Osikomaiya, 23, was charged with human trafficking, prostitution and related charges. He is being held at the Baltimore County Detention Center on $200,000 bail.
Police said a 16-year-old girl posted an online ad for prostitution and agreed to meet with an undercover officer at a motel.
Police found the girl at the motel and identified Osikomaiya as her pimp. He was taken into custody as he returned to the motel.
"At this point this is the only crime that he's committed that we know of," Baltimore County police spokesman Cpl. John Wachter said. "But obviously we're curious to find out if he's involved with anything else."
The victim, who has been previously reported missing, is not one of Osikomaiya's students. She is considered a victim and police said they are not charging her.