Castroneves grabbed the lead from Canadian Alex Tagliani after a round of late-race pit stops and held off a final charge from Sato, logging a victory margin of 0.84 seconds.
It was the second triumph of the season and 27th in the career for the Team Penske driver, who also took the March 25 season-opener in St. Petersburg.
The result also enabled Castroneves to grab second place in the IndyCar Series standings, moving to within 23 points of leader Ryan Hunter-Reay.
Will Power rallied from a 17th-place start to a third-place finish while Graham Rahal claimed fourth and Tagliani ended up in fifth place.
Notable deaths of 2014 [PHOTOS]