The 28-year-old Olympian posted 52.84, the fastest qualifying time in the 100-meter butterfly at the Arena Grand Prix Series in Mesa, Ariz., on Thursday.
He beat out former Team USA member Ryan Loche, who posted 52.94, the second fastest time in another heat.
Phelps' time would be enough for him to qualify for the men's butterfly at the U.S. national championships in August.
“You’re going to hear this word come out of my mouth a lot, but I was having fun," he told the New York Times.
Former Titans kicker dies in car crash
UPI Sports Results for September 20, 2014