The government says 68.8 percent of voters approved the law in a binding referendum Sunday. About 31.2 percent voted against it, the Associated Press reported.
Gay and lesbian couples will now be put on a par with heterosexual couples when it comes to inheritance, social security, immigration and taxation.
The new law is based on the Swiss model which came into effect in 2007 and therefore excludes the right to adopt children.
Parliament had all but adopted the legislation earlier this year but its critics, the group Vox Populi, called for a public poll.