He was consecrated the 5th Bishop of the Diocese of Tiraspol on 28 October 1904 and took residence in the diocesan headquarters in Saratov.

While Josef Kessler was Bishop of Tiraspol, the pastoral life of the diocese became successful and vital.

Bishop Kessler expanded the seminary, founded a publishing house, supported the work of male and female religious orders, visited all parishes of the giant diocese, and conducted 75,000 confirmations.

[1] On 14 August 1918, before the Bolsheviks captured Saratov during the Russian Civil War, Bishop Kessler fled the city on foot, and went to Odessa.

The Bishop secretly left Russia for Bessarabia (today divided between Moldova and Ukraine), where he was a priest in the village of Krasne near Tarutino.