Toronto acquired forward Amir Johnson and guard-forward Sonny Weems and sent Roko Ukic to Milwaukee along with Delfino, who spent last season in Russia.
Toronto retained Delfino's rights when he played in Russia last season but had to sign and trade the Argentine swingman to acquire Johnson.
NBA front-office sources told ESPN.com's Marc Stein on Tuesday that Delfino agreed to a three-year deal with the Bucks worth $10.5 million, but the second season of Delfino's new contract is only partially guaranteed and the third season carries no guaranteed money.
"Carlos made it clear he would prefer to play elsewhere if he were to return to the NBA," Raptors president Bryan Colangelo said in a statement. "There were limited sign and trade scenarios available, but acquiring Amir Johnson in this deal gives us another long, talented young big man whose best basketball is ahead of him."
Johnson spent the past four seasons in Detroit before getting dealt to Milwaukee in June. He appeared in 62 games for the Pistons last season and shot a team-best 59.5 percent while averaging 3.5 points, 3.7 rebounds and 0.97 blocks.
Weems appeared in 14 games as a rookie with the Denver Nuggets last year.
Delfino appeared in 82 games with the Raptors in 2007-08, averaging 9.0 points and 4.4 rebounds. Ukic made his NBA debut last season following six seasons overseas. He averaged 4.2 points, 2.1 assists and 12.4 minutes in 72 games.
Information from The Associated Press was used in this report.