Thomas played college basketball for the Indiana Hoosiers, leading them to the 1981 NCAA championship as a sophomore and declaring for the NBA draft.

He started playing basketball at age three and would dribble and shoot baskets as the halftime entertainment at Catholic Youth Organization games.

[3][4] Playing under coach Gene Pingatore, he led St. Joseph to the state finals in his junior year and was considered one of the top college prospects in the country.

[5] When Knight visited the Thomas home, one of Isiah's brothers, who wanted him to attend DePaul, embarrassed him by insulting the Indiana coach and engaging him in a shouting match.

When a Purdue player took a cheap shot at Thomas during a game at Bloomington, Knight called a press conference to defend his star.

[22][23] After taking a 3–2 series lead back to Los Angeles, Detroit appeared poised to win their first NBA title in Game 6.

[24][25] In the 1988–89 season, Thomas, along with teammates Joe Dumars, Rick Mahorn, Vinnie Johnson, Dennis Rodman, James Edwards, John Salley, Bill Laimbeer, and Mark Aguirre, guided his team to a 63–19 record.

After sweeping the Pacers and defeating the Knicks in five games, Thomas and the Pistons faced a tough seven-game series against the Bulls in the Eastern Conference Finals.

[32] Thomas has ridiculed the idea that he masterminded the supposed freeze-out as "ludicrous", pointing out that he was a relatively young player on a team that included Larry Bird, Julius Erving and Moses Malone.

With 7.9 seconds remaining in the fourth game, Laimbeer organized a walk-out and Thomas and all of his teammates—except Joe Dumars and John Salley—walked off the court, refusing to shake hands with the Bulls.

[41] Despite his talent, Thomas was left off the original Olympic Dream Team, possibly as a result of an alleged feud with Michael Jordan.

[44] Thomas is the founding chairman and CEO of Isiah International LLC, a holding company with a diverse portfolio of business ventures and investments.

[45][better source needed] In 1998, Thomas founded a company serving consumers, retailers, and corporations with online gift certificates and other i-commerce products.

[52] Thomas has served as CEO and executive chairman of the board of directors of One World Products, a cannabis company based in the U.S. with cultivation and processing facilities in Colombia.

[56] After leaving the Raptors, Thomas became a television commentator (first as the lead game analyst with play-by-play man Bob Costas and then as part of the studio team) for the NBA on NBC.

"[58] Thomas also launched a partnership between the CBA and SEASONTICKET.com to bring personalized video highlights and scores to fans across the country as well as be a portal for All-Star League voting.

Thomas attempted to bring up young talents such as Jermaine O'Neal, Jamaal Tinsley, Al Harrington, and Jeff Foster.

In his last year with the Pacers, Thomas guided them to a 48–34 record in the regular season and coached the Eastern Conference team at the 2003 NBA All-Star Game.

During the following season the Knicks became embroiled in a brawl with the Denver Nuggets that Thomas allegedly instigated by ordering his players to commit a hard foul in the paint.

During the 2007 NBA draft, Thomas made another trade, acquiring Zach Randolph, Fred Jones, and Dan Dickau from the Portland Trail Blazers for Steve Francis and Channing Frye.

Thomas also compounded the Knicks' salary-cap problems by signing fringe players such as Jerome James and Jared Jeffries to full mid-level exception contracts.

He was officially "reassigned" on April 18 "after a season of listless and dreadful basketball, a tawdry lawsuit and unending chants from fans demanding his dismissal".

[76] According to the New York Daily News, "nearly every major media outlet panned the announcement of Thomas' hire", and it led to a "public outcry" among fans.

Under Thomas's leadership as team president, and with his former Pistons teammate Bill Laimbeer as head coach, the Liberty finished first in the Eastern Conference during the 2015 season.

Mary's Court has teamed up with another Chicago-based charity, Kids off the Block, to serve meals to Chicago children and families during Thanksgiving.

[103] In September 2012, Thomas co-hosted the Ballin' for Peace Tournament at St. Sabina Church in Chicago to reduce gang violence through communication and basketball.

The New York City Peace Game featured over 50 players from across all five boroughs that competed in a tournament as well as a brief speaking program with special guests that included Harry Belafonte.

[109] Each year, Mary's Court provides gifts, clothing and educational items to hundreds of children in Chicago at its Holiday Toy Giveaway.

[110] On February 13, 2017, Thomas was presented the AT&T Humanity of Connection Award at the Smithsonian's National Museum of African American History and Culture in Washington, D.C.

[111] Thomas met his future wife, Lynn Kendall, the daughter of a Secret Service agent and a nurse,[112] in the early 1980s while they were both attending Indiana University.