By a vote of 56 to four, Luxembourger lawmakers passed a gay-marriage bill June 18 that also grants same-sex couples adoption rights.
The law is expected to be in effect by early 2015.
“All we have done is give equal rights to gay people. We formally recognize a form of relationship that has always existed,” Green Party MP Viviane Loschetter is quoted as saying.
Roy Reding, of the right-of-centre Alternative Democratic Reform Party, one of four MPs who opposed the measure, said marriage has been ruined.
The country’s prime minister, Xavier Bettel, and deputy prime minister, Etienne Schneider, are both gay. Bettel, who took the oath of office last December, had made the legalization of gay marriage one of his priorities.