The Initiative for Strategic Litigation (ISLA) in Africa said that the three had been "deported earlier this evening", in the statement dated Friday.
The lawyers were amongst a group of 13 people, including a Ugandan and Tanzanians, who were arrested last Tuesday at the Peacock hotel in Dar es Salaam.
Local police chief Lazaro Mambosasa said they had been "promoting homosexuality".
"Tanzanian law forbids this act between people of the same sex, it is a violation of our country's laws," said Mambosasa.
Just days later an NGO, the Community Health Education Services and Advocacy (CHESA) centre, was suspended on the same charge and accused of organising a workshop at the Peacock hotel.
CHESA and ISLA insisted they were merely coordinating a "legal consultation" to challenge a government decision to limit the provision of some health services.
In February, Tanzania provoked criticism notably from the United States after announcing the closure of several health centres specialising in AIDS prevention, alleging they were fronts for promoting homosexuality.
Tanzania has vowed to deport foreigners campaigning for gay rights in a country where gay male sex is punishable by anything from 30 years to life imprisonment.
In July 2016, the government banned the import of some lubricant gels alleging they were used exclusively by homosexuals.
Health Minister Ummy Mwalimu said the sale and occasional free distribution of the gels encouraged gay sex.
According to Amnesty International, homosexuality is illegal in 38 of 54 African states and is punishable by death in Mauritania, Somalia and Sudan.
Uganda repealed a 2014 move to impose the death penalty on gay people.
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