Titled "A Family Affair", the 10th Athens Pride held on central Klafthmonos Square was supported by nearly a dozen embassies including those of Britain, the United States and Canada.
"This year, we focus on the concepts of equality and freedom of choice from the perspective of family life as defined by every LGBT person, and specifically on the legal recognition of all LGBT families," the organisers said.
Homosexuals in Greece have begun seeking greater visibility and voice in recent years, holding the country's first Gay Pride event in 2005.
"Yesterday in the closet, today on the streets, tomorrow with our children," read a banner carried by one group of participants.
"Motherhood has no sexual orientation," said another.
Greek law on civil unions makes no specific provision for homosexual couples, and the first known same-sex civil marriage held in 2008 was annulled by a court a year later.
The case brought Greece before the European Court of Human Rights, which condemned the staunchly Orthodox Christian nation last year for creating a "life partner" legal category excluding gays.
The influential Greek Orthodox Church officially frowns upon same-sex relations, and its previous head archbishop Christodoulos famously condemned homosexuality as a "defect".