Democratic Gov. Maggie Hassan said she looks forward to signing the bill, which could be as soon as this week.
"This bipartisan plan is a uniquely New Hampshire solution and it exemplifies New Hampshire's tradition of collective problem-solving, demonstrating what is possible when we remain focused on solutions and reach across the aisle to achieve progress for our people," Hassan said in a statement.
New Hampshire is one of six states that had not decided whether to expand Medicaid under the federal law.
The bill passed the Senate on a bipartisan vote, but most House Republicans voted against it. The Democratic-led House rejected nine Republican amendments, including ones to cap the program and block its implementation until federal permission is received to spend Medicaid money on private health coverage.
The program is projected to cost $340 million a year when fully implemented and would use 100% federal funding through 2017 to expand the health care coverage. Adults up to age 65 could qualify, and supporters said the bill would improve the health of currently uninsured residents by providing access to affordable preventive and primary care. They said that would reduce the amount of uncompensated care provided by hospitals, which could help drive down premium costs and help struggling businesses.
Rep. Robert Elliott, one of the few Republicans to support the bill, said providing health coverage to the poor was the right thing to do and chided Republicans who opposed it.
"The public will perceive that we Republicans are opposed to the poor," said Elliott of Salem.
Opponents argued the state's financial liability should be capped to protect taxpayers.
"The numbers we have are guesstimates at best. We have no idea how many working age adults will apply for this," said Rep. Laurie Sanborn (R-Bedford).
House Republicans tried unsuccessfully to get the House to amend the Senate bill to cap the program at 60,000 people or $400 million in annual spending.
The state estimates that 12,000 adults could begin receiving coverage in as little as a month under an existing program to subsidize employer-based coverage while 38,000 others would receive coverage through the state's Medicaid managed care program starting July 1 or as soon as possible after that.
Under the proposal, the state would seek a federal waiver by March 31, 2015. While waiting for the government to act, about 38,000 adults could start enrolling around May 1 for coverage that would begin July 1 in the state's Medicaid managed care program. If the waiver is denied, their coverage would be phased out over three months.
With a waiver, New Hampshire could begin using federal Medicaid money to buy private insurance in 2016 through the federal marketplace for the 38,000 people on managed care.
The federal government would pick up the full cost until 2017. The expansion would end when federal funding drops below 100% unless the Legislature voted to continue it. The entire program also would end at the end of 2016 if the Legislature failed to reauthorize it.
The plan also would provide coverage to another 12,000 people eligible through an existing state program that subsidizes employer-based coverage. The Medicaid funding would pay for their coverage until 2017. Their coverage also would end if federal funding dropped below 100%.