Its first diocesan bishop, Vincent Valentine Ezeonyia, CSSp, was installed on 2 July 1990 at Christ the King Church; he was ordained bishop on 1 July 1990 at Mater Dei Cathedral in Umuahia.

At the time the Catholic Diocese of Aba was created, there were 24 parishes, 33 Indigenous priests, including those born and bred in Aba, many religious people, and a Catholic population of 227,225.

The bulk of the Catholic population was concentrated in Aba Urban and its immediate environs.

At some time after he took over the diocese had 144 priests, with 59 parishes, with several men in seminaries, and women in convents.

The bishop of the diocese, Vincent Valentine Ezeonyia, the clergy and lay faithful held a diocesan "Synod for True Christian Identity", holding sessions in 2001.