In late 2017, Dundon became involved in purchasing the Carolina Hurricanes of the National Hockey League from owner Peter Karmanos Jr. who had owned the team since it was the Hartford Whalers.^[8] Dundon became majority owner of the team on January 11, 2018, in a transaction where he purchased 52% of the team and the operating rights to PNC Arena for $420 million.^[9]

On June 30, 2021, Dundon completed the purchase of all minority shares in the team, leaving him as the sole owner of the Hurricanes franchise.^[10]

On March 5, 2026, Dundon finalized a sale of 12.5% of the Hurricanes to investors Brett Jefferson, Bobby Farnham, and Marc Grandisson at a $2.66 billion valuation.^[11][12]

Under the helm of Dundon, the Hurricanes made it to the Stanley Cup Final for the first time since 2006 following an Eastern Conference Final victory and won the Stanley Cup Final in June 2026 with a series score of 4–2.^[13] Dundon drew criticism after having his own name, along with those of his wife and five children, engraved on the Stanley Cup ahead of the players' names. The placement was considered unusual, as previous Stanley Cup-winning owners had not included family members' names on the trophy. ^[14] In the only other instance of a family member's name being engraved on the Stanley Cup, where then-owner of the Edmonton Oilers Peter Pocklington had his father's name engraved, the name was removed by the Hockey Hall of Fame.^[15]

On February 19, 2019, the Alliance of American Football announced a $250 million investment by Dundon and named him as a member of the board of directors.^[16][17] The cash infusion is believed to have saved the league from a short-term financial crisis.^[18][19] Reports noted that Dundon reserved the right to end his investment at any time.^[20][21]

Dundon's first publicly visible move as a member of the board of directors, was to move the AAF's championship to the Ford Center at the Star in Frisco, Texas, after meeting with Dallas Cowboys owner Jerry Jones and negotiating the change in venue. The move was an effort to align the AAF with the NFL. While the game had originally been scheduled for Sam Boyd Stadium in Nevada and ticket refunds had to be issued, the AAF's local partners were reportedly "understanding" of the venue change.^[22] Dundon later expressed concern for the future of the AAF if the National Football League Players Association was unable to share players. The NFLPA was reportedly reluctant to share players because of injury concerns.^[23]

The AAF suspended operations on April 2, 2019.^[24]

On December 27, 2021, Dundon's investment firm Dundon Capital Partners acquired Pickleball Central, the largest online pickleball retail site in the world. The acquisition also included Pickleball Central's affiliated PickleballTournaments.com software.^[25]

On October 5, 2022, pickleball.com launched, citing an investment from Dundon.^[26][27] The platform seeks to "bring together the data, content, and expertise" of the PPA Tour, the professional tour of pickleball, Pickleball Tournaments and Pickleball Brackets, the leaders in tournament and club software, TopCourt, a leader in online pickleball and tennis instruction, and Pickleball Central, the leading pickleball e-commerce platform.^[28]

On November 9, 2022, Major League Pickleball announced a strategic merger with the PPA Tour's VIBE Pickleball League. "Coming together as one team league allows us to build much bigger events, offer more prize money, enhance player development, pursue larger media and sponsorship deals and, most importantly, grow the game we all love", Dundon said in a joint announcement with Major League Pickleball's Steve Kuhn.^[29]

On August 13, 2025, Dundon and a group of investors agreed to purchase the Portland Trail Blazers of the National Basketball Association from the estate of Paul G. Allen for approximately $4.2 billion.^[30][31] On March 30, 2026, the NBA Board of Governors approved the sale for $4.25 billion.^[32]

Famously nicknamed "El Cheapo," Dundon reportedly refused to let two-way players travel with them in the postseason, cancelled traditional free playoff T-shirts for fans at home games and cut one of the team's two mascots to save nominal amounts of money. He also refused to pay for the team's late check out at a hotel during a play off play-in game, and the team masseuse was forced to massage the players in the lobby of the hotel. ^[33] He was also criticized for discussing the Blazers head coaching situation during the 2025-26 NBA season while interim head coach Tiago Splitter was leading the team to the playoffs, as well for his hiring of Micah Nori at below-market rate for a head NBA coach, and for the structure of Nori's contract, which only includes a single guaranteed year.^[34]