 On April 7, 1992, he was appointed Titular Bishop of "Maura" and an Auxiliary Bishop of Rome.Dieci received his episcopal consecration on the following April 26 from Pope John Paul II himself, with Cardinals Franciszek Macharski and Angelo Sodano serving as co-consecrators.As an auxiliary of Rome, he assists the Cardinal Vicar, currently Agostino Vallini, in the day-to-day administration of the diocese, which is delegated to him by the Pope.