Phelps, who retired after the 2012 Games with a record 22 Olympic medals -- a staggering 18 of them gold - launched his comeback last month in Mesa, Arizona, where he won his 100m fly heat but finished runner-up in the final to US Olympic teammate Ryan Lochte. (Agencies)
On Friday, Phelps led at the 50m mark and won in 52.13sec, with Pavel Sankovich of Belarus second in 52.72 and Singapore's Joseph Schooling third in 52.95.
The American superstar's winning time was the exact same time he produced in his runner-up finish to Lochte.
"I guess the consistency is there, still the walls were really bad," Phelps, 28, said of the rustiness in his technique at the turn and finish.
"I'm still having a tough time judging that wall at the 50, so that's something that I have to spend more time on," Phelps added.
Phelps also swam in the 200m freestyle heats on Friday morning, squeezing into the final but opting not to swim it in the evening.
He didn't look overjoyed in his post-win interview, but for now, he said, consistency and a 200m free time that will allow him to swim the event at the US championships in August, if he chooses, are enough.
"It's fine, being able to have a decent 200 (free) and just kind of get back to stroke is really what we want to do the most," he said.
Next up for Phelps is altitude training led by famously demanding coach Bob Bowman in Colorado.
"We spend about a month in Colorado," Phelps said. "I know it's good for me, but it's not always something I enjoy the most."
Phelps and Bowman have always been cagey about the swimmer's long-term plans, even when they were plotting the campaign that saw him win an unprecedented eight gold medals at the 2008 Beijing Olympics.
They have yet to confirm that with this return Phelps has his sights set on the 2016 Rio Games. August's US nationals in Irvine, California, could be a better gauge of Phelps's intentions.
That event serves as the American qualifying meet for next year's world championships in Russia, the last major full global showdown in the pool before Rio.
Phelps, who retired after the 2012 Games with a record 22 Olympic medals -- a staggering 18 of them gold - launched his comeback last month in Mesa, Arizona, where he won his 100m fly heat but finished runner-up in the final to US Olympic teammate Ryan Lochte.