The 32-year-old Agassi lifted the trophy at the Los Angeles Tennis Center for the third time in five years. He won in 1998 and trounced his long-time rival, Pete Sampras, a year ago.
"I got better with each match and just feel great about my game right now," Agassi said. "I couldn't be happier with the way the summer started."
In capturing his 53rd career ATP title, Agassi also became the 10th player in the 75-year-history of this event to win a third crown. He joined Fred Perry and Don Budge in the 1930's, Frank Parker and Jack Kramer in the 1940's, as well as Pancho Gonzalez, Vic Seixas, Roy Emerson, Arthur Ashe and Jimmy Connors.
Agassi, who collected the $51,500 first prize, dispensed with Gambill for the second time in as many career finals encounters. He also posted a straight-sets victory over the 25-year-old in the championship match at the 2000 Tennis Masters Series event in Miami.
"Andre was too tough," Gambill said. "He didn't make any errors. He ran me from side to side. I felt like a rag doll out there."
Gambill also was the runner-up here in 2000, falling to fellow countryman Michael Chang.
Agassi recorded service breaks in the second and seventh games to take the opening set.
He broke Gambill's serve for the fourth time to grab a 5-4 edge in the second before serving out the match.
"I was pretty close to blowing it open at 5-2," Agassi said. "When he held there and he picked up his game, next thing you know it's 4-4. A lot could happen from that point."