He also served as a priest at Vishniovka-Ashaly, collaborator of the apostolic nunciature and teacher of theology at the major seminary of Karaganda from 2007 to 2009.

He became the spiritual director of the inter-diocesan Mary the Mother of the Church seminary in Karaganda.

He was appointed vice-rector of the college at Guastalla Monza and Diocesan Assistant of Communion and Liberation from 2010 to 2012.

On the Solemnity of St Ambrose, 7 December 2012, Pope Benedict XVI appointed Dell'Oro Apostolic Administrator of Atyrau, Kazakhstan (upon the resignation of Bishop Janusz Wiesław Kaleta) and Titular Bishop of Castulo.

On 31 January 2015, Dell'Oro was appointed Bishop of Karaganda by Pope Francis[3][7] although he remained as Apostolic Administrator of Atyrau until 16 May.