The 18-time Olympic gold medalist will not serve time in jail, but he will be prohibited from drinking alcohol during his 18-month probation, according to local reports.
Maryland Transit Police stopped Phelps on September 30 after radar caught him going 84 miles per hour in a 45 mph zone. Reports say his blood-alcohol level was 0.14, nearly twice the legal limit of 0.08.
Phelps, 29, is thought to be preparing to return to swimming as the 2016 Olympics, which will begin one month after his probation is up. He is currently under a six-month suspension from USA Swimming.
Phelps previously pleaded guilty to DUI in 2004 at the age of 19. He received 18 months' probation before judgment, meaning the record could be expunged .