Pagenaud held the late lead but lost it to Power following a final pit stop on lap 70. He challenged for advantage in the final laps but Power hung on to win his second straight IZOD IndyCar Series.
The Australian also tasted victory two weeks ago at Barber Motorsports Park. His Sunday triumph gave Team Penske a 3-0 record after three events in the young season.
James Hinchcliffe finished third at Long Beach, Tony Kanaan came in fourth and J.R. Hildebrand rounded out the Top 5.