On February 10, 2020, the Red Sox traded Betts, David Price, and cash considerations to the Los Angeles Dodgers in exchange for Alex Verdugo, Connor Wong, and Jeter Downs. On July 22, the Dodgers signed Betts to a 12-year contract extension, through the 2032 season. The deal was worth $365 million and also included a $65 million signing bonus, making it the richest contract in Dodgers history, and the third-richest contract in the history of North American sports.
The 2020 season was delayed and shortened from 162 games to 60 due to the COVID-19 pandemic. On July 23, Betts was the starting right fielder, making his Dodgers debut on Opening Day against the San Francisco Giants, getting his first hit, a single, as a Dodger against pitcher Tyler Rogers. On July 31, Betts hit his first home run as a Dodger against Arizona Diamondback pitcher Zac Gallen. On August 14, Betts hit three home runs against the San Diego Padres, his sixth three-homer game of his career, tying Sammy Sosa and Johnny Mize as the only players in MLB history to accomplish this feat. Later that month, Betts hit two home runs and stole two bases against the Colorado Rockies, becoming only the 19th player—and first Dodger—to have a multi-homer, multi-steal game. On August 27, 2020, he reached 1,000 MLB career hits.
Betts finished the 2020 season hitting .292/.366/.562 with 47 runs (4th in the NL), 16 home runs (3rd), 39 RBIs, a .928 OPS, and 10 stolen bases. He won his second World Series in a three-season span after the Dodgers defeated the Rays in the 2020 World Series. After the season, Betts was awarded his fifth consecutive Gold Glove (first in the National League) and his fourth Silver Slugger. He finished second in NL MVP voting behind Freddie Freeman of the Atlanta Braves.