After a first rejection in 2014, a synod voted Monday 83 to 29 in favour of a new liturgy, or service, that will be available as of February 1st. It will serve in addition to one that blesses heterosexual couples.
Each pastor will be free to choose whether or not to marry same-sex couples.
"It is the day when a prayer and a dream came true," the leader of the liberal wing of the Lutheran Church, Gard Sandaker-Nilsen -- himself gay -- told NTB news agency.
The Swedish, Danish and French Protestant churches are among others that already allow such ceremonies.
Last year, a previous synod voted in favour of celebrating same-sex marriages, but the Church needed to adopt a special liturgy before gays could marry in church.
In 2015 about 73 percent of people in Norway were registered as members of the Church, which separated from the state on January 1st.
Like its Nordic neighbours, Norway is at the forefront of gay rights in Europe. Civil marriage and adoption have been open to gays since 2009 and the Church also authorises the ordination of homosexuals.