A meeting of delegates passed the bill which will see gay weddings take place in the churches.
On Monday 88 delegates out of 115 in total backed the proposals.
Gard Sandaker-Nilsen, the man who brought the proposal forward, said: "Finally we can celebrate love independently of whom one falls in love with".
Priests with an objection to same-sex marriage will have a right to refuse to be involved.
Norway has been many years ahead other parts of the world in advancing rights for LGBTI people.
It passed same-sex partnership laws in 1993, become the second country in the world to do so.
The vast majority of Norway's Christians are members of the Lutheran Church.