The 33-year-old athlete said Wednesday he is "enjoying every moment" in London.
Parsons was America's best hope for a whitewater medal in the K-1, or one-man kayak class, in the Beijing Games. He missed a gate and came in 20th. He announced his retirement shortly after, just as he had done following the 2004 Athens Games.
"It was a mistake both times on my part," he said, adding that as soon as he took time off to think, he realized how much he enjoyed the sport.
The London Olympic course is "pretty fantastic," Parsons said. It's in "nice, clear water so you can see all the obstacles and avoid injuries and broken boats."
Parsons joins Caroline Queen, sprint kayakers Carrie Johnson and Tim Hornsby at the London Games. Casey Eichfeld will represent the Americans in single canoe, while Eric Hurd and Jeff Larimer will compete in double canoe.