Phelps presented cops with an expired Michigan license and admitted he guzzled a beer about an hour and 15 minutes before his SUV made contact with another driver who ran a red light, police told the Associated Press.
Officers didn't give Phelps a sobriety test, but instead slapped him with the two charges. He won't be fined, but Phelps must appear in Maryland courts to explain his license's expiration.
The female driver of the Honda Accord involved in the accident was "shaken up'' and taken to a local hospital as a precaution, police said. She ran a red light and crashed into Phelps' Cadillac Escalade, said police spokesman Anthony Guglielmi. It's unclear if she's been issued a citation.
Phelps' two passengers were not injured, Guglielmi said.
Phelps and his passengers were all wearing Baltimore Ravens jerseys, but it was not immediately known if he was at the Ravens-Redskins game before the crash. The crash happened at about 9 p.m.
Guglielmi initially said that the Olympic gold medal swimmer was interviewed by police and that alcohol was not a factor.
Phelps' SUV had a crumpled hood and was on a tow truck. The gray Accord had considerable damage on the front driver side.
Phelps has had brushes with the law in the past. USA Swimming suspended him earlier this year for three months after a British tabloid published a photo of him using a marijuana pipe. The Richland County, S.C., sheriff's office investigated the photo but found there wasn't enough evidence to charge Phelps.
In an earlier incident, Phelps pleaded guilty to driving while impaired shortly after he won six golds and two bronzes at the 2004 Athens Olympics. A Maryland state trooper had pulled him over after Phelps ran a stop sign. He was sentenced to 18 months' probation.
Phelps won eight gold medals at the Beijing Olympics. Most recently he earned five golds and a silver over eight days at the world swimming championships earlier this month.