Close Hatches was second, 4 1/4 lengths behind the winner, with Authenticity third. Royal Delta, trying to win the race for the third straight year, contested the early lead but was struggling as the field reached the end of the backstretch. She finished fourth.
Princess of Sylmar, the nation's leading 3-year-old filly before Friday's race, finished last of six. Beholder had finished second to Princess of Sylmar in the Kentucky Oaks and divisional honors now are up for grabs.
Beholder, a Kentucky-bred daughter of Henny Hughes, sat just behind Authenticity and Royal Delta as that duo contested the early lead. On the stretch turn, Authenticity put away Royal Delta. But when veteran jockey Gary Stevens gave Beholder her cue, Authenticity had no answer.
Beholder finished the 1 1/8 miles on a fast and generally speed-favoring Santa Anita track in 1:47.77.
Since finishing fourth in her career debut, Beholder has posted eight wins and three seconds from 11 starts for trainer Richard Mandella. Among those wins were last year's Breeders' Cup Juvenile Fillies and this year's Grade I Santa Anita Oaks, both over the same track.
For Royal Delta, the fourth-place showing put an exclamation point on a disappointing year, which ends with two straight losses. She also was defeated in her last previous start -- by Princess of Sylmar.
Winning owner B. Wayne Hughes, asked about the championship implications of the race, said, "Champions are made by beating champions ... I think she's done enough."
Stevens came back from a lengthy retirement to resume riding this year. He picked up his ninth Breeders' Cup win, moving him into a tie with Chris McCarron for eighth place on that list.
The leading Breeders' Cup jockey, by both wins and earnings, Mike Smith, won the first two races on Friday's championship card, advancing his win total to 19.