Christie announced his acceptance in an address to the Legislature outlining a $32.9 billion budget for the fiscal year beginning July 1.
"Let me also be clear. I am no fan of the Affordable Care Act," Christie said. "I think it is wrong for New Jersey, and I think it is wrong for America."
He said that even though he believes the act will not "achieve what it promises," it is the law, and snubbing federal funding would only mean that other states would get the money.
As if to highlight his opposition to the act, Christie noted that he has rejected efforts to establish a state-run insurance exchange and instead has decided to allow the federal government to run the exchange in New Jersey.
Christie said the health-care expansion would benefit 104,000 residents. Other estimates have put the number as high as 300,000. About 1.4 million New Jersey residents are covered by Medicaid.
Assembly Speaker Sheila Oliver (D., Essex) said the Medicaid expansion was one bright spot in the budget, but suggested Christie politically had no other choice.
"There is no way in a state like New Jersey the governor could walk away from Medicaid expansion," she said.
Supporters of the act used words like momentous and commendable to describe Christie's decision, a turnaround that the governor said resulted from "considerable discussion and research."
Ethan Rome, director of Health Care for America, said Christie's action "sends a powerful message to every Republican governor and state lawmaker that it's time to stop playing games with people's lives and to fully participate in Medicaid."
Raymond Castro, senior policy analyst for New Jersey Policy Perspective, said Christie, "much like he did in the aftermath of superstorm Sandy, has demonstrated the leadership and independence of a governor who is willing to place the interests of New Jerseyans above partisan politics."
The decision by Christie and other governors has not prompted Corbett to change his mind, a spokeswoman said.
"The questions and concerns that the governor posed in his letter to HHS are still outstanding, and he remains concerned about the cost of expanding Medicaid in Pennsylvania without reforms," spokeswoman Christine Cronkrite said in an e-mail.
The Medicaid expansion will be 100 percent federally funded for the first three years. By 2020, states in the program will have to pick up 10 percent of the cost.
The Medicaid expansion originally was mandated by the Affordable Care Act, but the Supreme Court last year ruled that states could opt out.
New Jersey will save $227 million next year under the expansion, the Christie administration said.
Starting in January 2014, the program will provide Medicaid coverage to single New Jersey residents 19 to 65 who make less than $16,000 a year.
According to a Kaiser Family Foundation estimate, the expansion will cost New Jersey $533 million over the first five years. According to federal government projections, Washington will funnel more than $9 billion into the state during the same period.
Contact Joseph A. Gambardello at 856-779-3844 or firstname.lastname@example.org
Inquirer staff writer Angela Couloumbis contributed to this article.