The vote, coupled with the state Senate's 14-7 override during the weekend, means the bill becomes effective Oct. 1, the Las Vegas Review-Journal reported Monday.
Under the law, couples -- whether same sex or opposite sex -- can sign a registry at the secretary of state's office, then pay a fee for a domestic partnership contract that essentially gives them the same legal rights and responsibilities as married couples, the newspaper said.
Employers are not required to offer healthcare and other benefits to domestic-partner couples, but may if they wish.
"I'm immensely pleased that the veto of the governor has been overridden," said state Sen. David Parks, the bill's chief sponsor. "It's a great day for fairness and equality in Nevada."
Domestic partnerships, or civil unions, aren't the same as same-sex marriages, legal in five states. Nevada voters in 2002 approved a constitutional amendment specifying that a marriage can be between only a man and a woman.
Conservative activist Richard Ziser, who led the drive for the constitutional amendment, said his supporters would review their options before deciding on a next step.