Same-sex civil partnerships and giving gay couples right to adopt was legalized after Malta's parliament passed a law on Monday.
The Mediterranean island country's parliament passed the bill by a vote of 37-0.
The opposition abstained because it opposes gay adoption but not gay unions, said its leader Simon Busuttil.
Thousands of supporters cheered the law's passage on the central square in the capital Valletta.
Catholicism is the state religion in Malta, the European Union's smallest member state.
International Lesbian and Gay Association, which welcomed the new law, believes that Malta is the 22nd European country to recognize same-sex unions and the 10th to allow such couples to adopt.