Dixon, who outpaced Sebastien Bourdais in a two-lap sprint to the finish Saturday, had a much easier time in Sunday's second race on the 1.75-mile, 11-turn street circuit.
He passed current IndyCar points leader Helio Castroneves after a late accident involving Ed Carpenter had necessitated another two-lap sprint to the finish, claiming his third consecutive victory overall -- Dixon also won last week's event at Pocono Raceway.
The Chip Ganassi Racing driver pocketed a $100,000 bonus for claming both weekend races and pulled to within 29 points of the IndyCar lead.
Castroneves garnered second place, followed by Bourdais, Dario Franchitti and E.J. Viso.