Scott O'Neil, the chief executive of the Josh Harris-owned teams, and Norbert Teufelberger, the chief executive of bwin.party digital entertainment that operates partypoker, confirmed the multiyear agreement in a statement Wednesday night.
A news conference was scheduled for Thursday at the Prudential Center to formally announce the deal.
Bloomberg was first to report the deal.
New Jersey authorized Internet gambling last year to give a boost to Atlantic City's struggling casino industry, which has been beset by increasing competition for the past seven years. It began with a five-day trial period on Nov. 21 and launched publicly on Nov. 25.
As of Monday, 148,487 accounts had been created, though the state's Gaming Enforcement Division notes that individuals often create separate accounts on more than one site.
"We are proud to welcome partypoker to our family as we embark on an exciting journey with an innovative, global leader in the digital marketplace," O'Neil said. "As an organization, we will continue to align with brands that aspire to grow with us, in true partnership."
Teufelberger said his company was excited to offer Devils and Sixers' fans great digital content and unique game-day experiences.
"They are two of the most iconic names in American hockey and basketball with huge and loyal fan bases throughout New Jersey and the surrounding metropolitan areas," Teufelberger said. "There is an affinity between playing in online poker tournaments and sports - winning is about having intense focus, stamina and a great competitive spirit."
Neither the NHL nor the NBA had a problem with the teams having a sponsorship agreement with an online gambling company.
"As long as the gambling site doesn't include sports gambling or sports betting, it's now allowed within our rules," NBA vice president Mark Tatum said in a statement sent by the league to The Associated Press.
Online betting marks the biggest expansion of gambling in New Jersey since the first Atlantic City casino opened in 1978. The state lets gamblers play any of the games offered in its 12 casinos including card games and slots, but online poker has proven especially popular in the early going.
New Jersey is the third state in the nation to offer Internet gambling, after Nevada and Delaware.
It remains to be seen if the $200 million to $300 million that Wall Street analysts predict Internet gambling may bring in over its first year will be new business, or whether it will simply cannibalize walk-in business at the brick-and-mortar casinos.
Harris and business partner David Blitzer bought the Devils and the lease to the Prudential Center from Jeff Vanderbeek for $320 million this summer.
A New York-based leveraged buyout specialist, Harris bought the Sixers from Comcast-Spectacor in 2011. Blitzer, a senior managing director of The Blackstone Group, was also in that group along with Art Wrubel and Jason Levien.
Associated Press writer Wayne Parry contributed to this report.