The deal was agreed to Saturday afternoon after Anthony waived his no-trade clause ahead of the NBA Media Day on Monday.
The 6-foot-8, 240-pound Anthony, a 10-time All-Star and 14-year NBA veteran, joins the Thunder having appeared in 976 career games (all starts) while averaging 24.8 points, 6.6 rebounds, 3.1 assists and 1.1 steals.
"We are thrilled to welcome Carmelo to Oklahoma City and the Thunder organization," Thunder general manager Sam Presti said in a statement. "In addition to his skill level, experience, and unique talents, Carmelo is another high character, professional player for our roster."
The 33-year-old Anthony waived his no-trade clause and his $8.1 trade kicker to accommodate the deal. He has two years and $54 million left on his contract, including a player option for $27.9 million on the 2018-19 season.
"This is a deal we feel works for both this franchise and Carmelo," Knicks president Steve Mills said. "We thank him for his seven seasons in a Knicks uniform and all that he accomplished off the court for the City of New York by using his platform to address social issues.
"We will continue to focus on this team looking forward towards the immediate and long-term future. As we have said recently, this is a new beginning for the New York Knicks."
The trade ends Anthony's 6 1/2 seasons in New York. The no-trade clause was part of the maximum contract that Anthony signed in 2014 and he declined a trade from the Knicks throughout the turmoil of Phil Jackson's tenure as president of basketball operations.
"Thank you to All My Fans who supported me through Thick and Thin," Anthony wrote in a letter to New York on his website. "And those who continued to support The Knicks regardless of the outcome. Thank You to Jim Dolan and the Knicks organization and all the hardworking people that don't get the credit they deserve. And most importantly, Thank you to the City of New York for allowing me to represent OUR city."
Anthony joins MVP Russell Westbrook and newly acquired All-Star forward Paul George in a reshaped and Western Conference contender. Both players reportedly played a significant role in recruiting Anthony to waive his no-trade clause for Oklahoma City.
Anthony was acquired by the Knicks from the Denver Nuggets on Feb. 22, 2011. He finished his Knicks career as the team's seventh all-time leading scorer with 10,186 points and No. 3 on the franchise's scoring average list at 24.7 points per game.
Anthony currently ranks 25th on the NBA's all-time scoring list (24,156 points) and he is one of six players in league history (alongside Kobe Bryant, Vince Carter, LeBron James, Dirk Nowitzki and Paul Pierce) to record 24,000 points, 6,000 rebounds, 2,500 assists, 1,000 steals and 1,000 3-point field goals.
Anthony led the NBA in scoring during the 2012-13 season (28.7 points per game) and during the 2009-10 season, he became the third youngest player in NBA history to reach the 12,000-point plateau (behind James and Bryant).
A three-time Olympic gold medalist, Anthony is the U.S. Olympic Men's National Team's all-time leading scorer.
Anthony helped lead Syracuse to a national championship during his freshman season in which he was named the Final Four's Most Outstanding Player. He was originally selected by the Nuggets with the third overall pick in the 2003 draft.
The 6-11, 245-pound Kanter is a six-year NBA veteran who holds career averages of 11.3 points and 6.7 rebounds in 445 games played for Utah and Oklahoma City. In 72 games for the Thunder last season, the 25-year-old Switzerland native averaged 14.3 points and 6.7 rebounds, while recording the second-most point-rebound double-doubles in the NBA off the bench with 18.
The 6-8, 225-pound McDermott is a three-year NBA who holds career averages of 8.0 points in 183 games played for Chicago and Oklahoma City. In 66 games for the Bulls and Thunder last season, the 25-year-old McDermott averaged 9.0 points and 22.8 minutes.
"We acquired two 25-year-old players in this deal that we can develop, while sticking with our overall strategy of emphasizing youth and athleticism," Knicks general manager Scott Perry said. "With this trade, we have added scoring and aggressiveness to our frontcourt, and bolstered the team's perimeter shooting. We are glad to have finalized a trade that made sense for all of us."