The 34-year-old guard also was honored as the league's best player off the bench while with the Atlanta Hawks in 2009-10.
Crawford led the league's reserve players in scoring this season, averaging 18.6 points. He came off the bench in 45 of 69 games he played in, helping the Clippers to a 57-25 record, their best regular-season mark in franchise history.
The Clippers had a 31-14 record when Crawford came off the bench this season. The Clippers and Oklahoma City are 1-1 in their Western Conference semifinal.
"I actually think he won it because I think voters saw him doing other things for the team — playing defense, running the team at the point guard position when Chris Paul was out at times," Clippers coach Doc Rivers said last week, when The Associated Press first reported that Crawford had won. "He's been the perfect utility player for a team. He's been awesome."
Crawford set the single-season franchise record for 3-pointers made with 161. That surpassed his record from last season, his first in Los Angeles, when he was runner-up for the Sixth Man award.
Crawford received 57 first-place votes and 421 total points from a panel of 125 sports writers and broadcasters throughout the U.S. and Canada. He joined Kevin McHale, Ricky Pierce and Detlef Schrempf as two-time winners.
Taj Gibson of Chicago finished second with 395 points and San Antonio's Manu Ginobili was third with 138.
Crawford had his best month in January, scoring in double figures in 15 of 16 games and helping the Clippers go 12-4 that month.
On Jan. 25, he had 37 points and 11 assists in a win over Toronto — the most points he scored off the bench in his career and his most with the Clippers. It was the second time this season he had that many points and assists; he totaled those numbers against Sacramento on Nov. 29.
Crawford missed 13 games in March and April because of injury.
The award sponsor, Kia, will donate a 2015 vehicle to a charity of Crawford's choice.