|This article does not cite any references or sources. (December 2006)|
Ubaldini was born in the Buenos Aires barrio of Mataderos, the son of a meat worker and a seamstress. He worked in the processing plants and became involved in the trade union. In 1969 he started work at a small yeast factory and seven years later he was elected the Secretary-General of the small union of beer-industry workers. During the Proceso dictatorship, he was elected general secretary of the CGT, the trade union umbrella body, in 1979. In the years that followed, he led the "Brasil" fraction of the CGT, which showed a harder line against the military than its "CGT Azopardo" counterpart. He led a march of 10,000 protesters against the dictatorship in 1981, the first large protest of that period.
When democracy returned, he became leader of the CGT in 1986. From this position he launched 13 general strikes against Radical Raúl Alfonsín's government.  However, the CGT's combativeness subsided once Peronism was back in power. In 1989 Ubaldini was displaced as head of the CGT by supporters of President Carlos Menem. Although he had backed Menem's election campaign publicly, Ubaldini opposed Menem's free market reforms and refused to vacate the CGT building. 
In 1993, Ubaldini stood to be Governor of Buenos Aires Province, heavily defeated by the Menemist Eduardo Duhalde. He was elected in 1997 and again in 2001 as a national deputy for Buenos Aires Province. In his last role he assisted the Planning Minister Julio de Vido. He had also been vice president of the international trade union movement CIOSL. 
He died of lung cancer, aged 69, in Buenos Aires.