The founder of one of the world's largest private equity firms, Harris and his group paid $320 million to Jeff Vanderbeek for the rights to the Devils and the lease to the Prudential Center.
The deal was announced Thursday morning after the attorneys for the two sides took about 15 extra minute to sign off on the transfer of the financially strapped three-time Stanley Cup champions.
Harris, whose main partner is fellow equities investor David Blitzer, needed roughly a week to close the deal after talks with Philadelphia attorney Andrew Barroway fell through.
The NHL's board of governors approved the deal on Wednesday.
Harris announced that Devils general manager and president Lou Lamoriello, who has been the architect of the team's three titles, will remain with the club.
Scott O'Neil, who serves as chief executive officer of the 76ers, will come to the Devils in the same role. He previously has spent four years with Madison Square Garden sports as chief executive.
Vanderbeek, who has been the majority owner of the Devils since 2004, will remain with the Devils as a senior adviser.
While Harris owns the 76ers, he leases space at the Wells Fargo Center from Comcast Spectacor, which also owns the NHL's Flyers. He also slammed the door on theories that he might move the basketball team to Newark.
"The Sixers are staying in Philly," Harris said.
Having the lease at the Prudential Center, Harris has a chance to earn money from concerts and other events, and he might leverage "The Rock" as a way to get a better deal in Philadelphia.
The Devils won the Stanley Cup in 1995, 2000 and 2003, and won additional Eastern Conference championships in 2001 and 2012. They missed the playoffs in the recent lockout-shortened season and were stunned when 30-year-old superstar forward Ilya Kovalchuk decided to play in his native Russia.
The Devils moved to New Jersey in 1982, playing at the Meadowlands after relocating from Colorado.