After his car was serviced, Castroneves was ready to pull away but was held by his crew an extra second or two so that Castroneves wouldn't collide with the car of Tony Kanaan, Dixon's teammate at Chip Ganassi Racing.
That enabled Dixon to drive past Castroneves and leave pit road with the lead he would hold for most of the remaining laps.
"It was better to be safe than sorry," Castroneves said of being held up.
Once they were racing again, "I was really pushing hard [to catch Dixon] but with his experience, I knew he wasn't going to make a mistake," Castroneves said.
Dixon's win was the 36th of his IndyCar career. Montoya won the season opener on the streets of St. Petersburg, Fla., on March 29, and James Hinchcliffe won a week ago on a road course near New Orleans. Hinchcliffe finished 12th at Long Beach.