Luis Juez was born in Córdoba, Argentina, to Adela Losada, the daughter of Spanish Argentine immigrants from A Coruña, and Gabriel Juez, the son of Arab Argentine immigrants from Syria. Encouraged by his father, a former Army officer, Juez studied at the General Paz Military Lyceum, though he ultimately opted against a military career, and enrolled at the National University of Córdoba. Juez, whose father had been jailed by the dictatorship that overthrew President Juan Perón in 1955, was active in the Peronist Youth, earning a "juris doctor" in 1985. He married the former Victoria Corte in 1992, and they had four children.