The Commonwealth Games champion clocked 23.70 seconds to beat Poland’s Konrad Czerniak and South Africa star Chad Le Clos.
Czerniak was second in 23.89 and Le Clos third with a time of 23.92. Fellow Brit Adam Barrett finished seventh in the final with 24.63 seconds.
Proud, swimming for Great Britain, had missed out on making the final of the 100m freestyle but he will be hoping for more success in the 50m free on Thursday.
Great Britain are using the event as preparation for this summer’s World Championships.
University of St Mark and St John student Proud said after the race: “That is the right time for me mid-season. I am just trying to be as powerful and clean as possible.
“It is good to race people I am going to be racing this summer.”