 He was ordained a priest on 25 July 1914 by Archbishop Ildefonso Pisani, and four months later, in November, traveled to Rome to study at the Pontifical Biblical Institute.When Italy entered World War I, Lercaro was forced to change posts and become a military chaplain until the war ended in 1918.In 1918, he became Prefect of the Seminary of Genoa, where his brother Amedeo was rector, and would remain in that post until 1923.