Harvick took the lead for the first time on lap 188 after Matt Kenseth and Johnny Sauter were involved in a brush-up.
"We didn't have a dominant car and won the race," said Harvick, who has three straight top-five finishes. "I'll take that any day."
With his pursuer cutting into his lead by about two-tenths of a second on every lap, Harvick kept his Chevrolet Monte Carlo in front of Kahne's Dodge Intrepid to notch his 12th career Busch series win and first at Las Vegas Motor Speedway.
Kahne, the pole-sitter for Sunday's Nextel Cup UAW-DaimlerChrysler 400, tried to make a move on the leader but was blocked on the apron by Harvick, who won by 0.119 seconds.