São Paulo state notaries are now obliged to recognize same-sex marriages.
According to Brazilian newspaper Folha de S. Paulo, this court ruling permits gay couples to obtain a marriage certificate without needing prior approval from a court.
This week's court order also means that same-sex couples already registered in a civil union do not need court approval to convert their status into marriage.
Recognition of civil marriages was the primary demand of the same-sex couples that participated in a mass civil partnership registration on 28 September 2012.
The measure will enter into force in 60 days, and serves as an important precedent for other Brazilian states and Latin American countries.
Brazil has rapidly advanced its gay marriage and civil unions laws in the past two years.
Brazil's Supreme Federal Court approved in 2011 for same-sex couples to receive the same rights as married couples through civil unions.
Earlier this year, a São Paulo judge approved what is considered to be the first gay marriage in the country.
In August 2012, Mario Domingos Grego, 46, and Gledson Perrone Cordeiro, 32, became the first homosexual couple, not already in a civil union, to be married in Brazil's largest city.
According to Brazilian lawyer Adler Martins, foreigners can also now come to São Paulo to obtain a marriage visa, which is easier than obtaining a civil union visa.
Countries permitting foreign marriages have become a recent trend in helping LGBT rights groups promote gay marriages outside their territories.
In 2012 both Uruguay and Argentina permitted the marriages of same-sex foreign couples within their borders, requiring only a temporary address and copies of their passports.
In Latin America, gay marriage is only legal in Argentina, Mexico City and now São Paulo, while same-sex civil unions are recognized throughout Colombia, Uruguay, Brazil and Ecuador.