Norway's Lutheran Church joined several other mainline denominations in the world and voted to allow same-sex marriages.
The church committee had put forward a draft resolution which read: "A majority of the Bishops' Conference believes that in addition to the current rituals for marriage and civil marriages between women and men, corresponding rituals must be devised that include couples of the same sex and that can be used for all couples."
At the NLC meeting, as many as 88 delegates out of 115 voted in favor of the change.
The proposal was earlier rejected at a convention in 2014.
According to the resolution, priests who do not wish to marry gay couples cannot be compelled to preside over the union.
Norway as a country has been open to gay unions for many years now. It legalized same-sex marriage in 2009, making it the second country to do so after Denmark, which legalized gay marriage in 2001 and legalized same-sex partnerships in 1993.
The NLC said that allowing same-sex unions in the church was a "historic decision that marks a shift in the church's teaching on marriage."
About 74 percent of Norwegians are adherents of Lutheran Church, according to the national statistics agency.
Last year the Presbyterian Church, U.S.A. (PCUSA) and French Protestant Church approved the gay marriages, and altered their organizational constitutions.