He enrolled at the Instituto Libre de Segunda Enseñanza, a public college preparatory school, and earned a law degree at the University of Buenos Aires.

His opposition to the pardons granted by President Carlos Menem to leaders of the 1976–83 dictatorship convicted in the 1985 Trial of the Juntas led to Ibarra's dismissal as prosecutor in 1991 by Solicitor General Oscar Roger.

Ibarra was elected on May 7, 2000, as Mayor of the Autonomous City of Buenos Aires in the first round, defeating Domingo Cavallo, former Economy Minister of the country.

On December 30, 2004, the República Cromagnon nightclub fire killed 194 people and raised a wave of accusations against political officials of the city.

He accused the opposition of manipulating the families of República Cromagnon's victims in order to ruin his career, and upon being notified of the suspension, he announced did not resign but await for the investigation to be concluded.