Roy, 82, the oldest runner participating in the half marathon, finished the course in three hours, 28 minutes and 40 seconds, clipping five minutes from his last US run in Alexandria, a Washington suburb in Virginia, last May.
More than 6,000 runners joined the half marathon taking them past several of the American capital's tourist sights, including the Washington Monument, the Lincoln Memorial and the National Mall.
Starting and finishing in the shadow of the Washington Monument, the race followed a picturesque route around the Tidal Basin and then along the Potomac River and crossing the Arlington Memorial Bridge before turning back.
A resident of Delhi's Chittaranjan Park, Roy makes his next run in the US in the Woodrow Wilson Bridge Half Marathon in Alexandria Oct 5 with his daughter.
Roy, who switched over to half-marathons after a spinal injury in November 2011, took to running marathons at the age of 52.
By the age of 75, he had completed 82 races and went on to complete his 100th marathon in January 2010.
A retired wing commander of the Indian Air Force, he ran his 115th marathon in Mumbai in January 2013.