The Yankees received right-handed reliever Diego Moreno and outfielder Exicardo Cayones in return for Burnett, whose tumultuous three-year stay in the Bronx appears to be over, according to the New York Daily News.
The Pirates will pay between $13-14 million of the $33 million remaining on Burnett's contract, the Daily News reported Friday.
The Yankees signed Burnett after the 2008 season, around the same time they also landed CC Sabathia.
But unlike Sabathia, who is 59-23 with the Yankees, Burnett has struggled to produce in the rotation and finished three seasons for New York with a 34-35 mark.
The trade, which hasn't been announced by the Yankees, is pending a physical by the 35-year-old Burnett and must also be approved by Major League Baseball.
Burnett helped the Yankees to a World Series title in 2009, but had been a disappointment after inking a five-year deal worth a reported $82.5 million. He was 13-9 with a 4.04 earned run average in his first season, but was just 21-26 with a 5.20 ERA the last two years.
The Yankees also have an abundance of starters vying for spots in the rotation heading into spring training. Sabathia, Ivan Nova, Phil Hughes and Freddy Garcia are returning from last season. New York also added Michael Pineda in a trade with Seattle and picked up Hiroki Kuroda as a free agent.
Burnett apparently first nixed a trade to the Angels that would have brought Bobby Abreu back to New York. He has a limited no-trade clause and reportedly wanted to stay closer to his Maryland home.
He has a career mark of 121-111 with a 4.10 ERA in 314 games, all but five of which have been starts. He broke into the majors with Florida in 1999 and pitched for the Marlins until leaving for Toronto in 2006.
After three seasons with the Blue Jays, Burnett opted out of his contract following a strong 2008 campaign. He was 18-10 with a 4.07 ERA that season, netting him the big contract from the Yankees.