Rui Tavares was born in Lisbon on 29 July 1972, to a bank clerk (and occasionally shepherd) father and a homemaker mother.

[3] The family was originally from the small rural village of Arrifana, in Azambuja, in the Ribatejo Province, where Tavares spent part of his childhood.

The Protestant denomination was indirectly introduced in the town by an atheist great-uncle of Tavares, who invited a Baptist pastor to the village to spite the Catholic hierarchy.

[7] Tavares had run alongside incumbent Mayor Fernando Medina on the electoral list of the "Mais Lisboa" coalition (Socialist Party and LIVRE), to be the councillor with the "Human Rights, Knowledge, Science, and Culture" portfolio on a Socialist-led City Council.

The majority, however, was won by the "Novos Tempos" coalition (PSD/CDS–PP/Alliance/MPT/PPM); Tavares stated his intention to serve as opposition within the City Council to the new centre-right Mayor, Carlos Moedas.