[2] Upon returning to Naples, Sforza made Sarnelli responsible for teaching canon law at the Archepiscopal Athenaeum and history at the Troise Lyceum.
Upon Petagna's death on 18 December 1878,[1] Sarnelli succeeded him as Bishop of Catellammare di Stabia, being officially appointed by Pope Leo XIII on 28 February 1879 and receiving his episcopal consecration on 2 March 1879.
[5] Shortly after becoming Archbishop of Naples, Sarnelli became ill and, on 2 January 1898, died and was buried in the cemetery of Santa Maria del Pianto .
It was said that during his time as bishop, Sarenlli never spent more than one lira per day, donating the rest of his income to the poor and the maintenance of the cathedral.
[1] On 7 January 1898, the vicar capitular of Naples, Carbonelli, placed Sarnelli's body in "canonical deposit", as was custom when there where tumultuous circumstances and a process of beatification was beginning.