He was ordained subdeacon at St Mary's College, Oscott on 19 December 1845, and deacon on 5 June 1846, and on 19 December of the same year was raised to the priesthood at Ratcliffe College. After some months devoted to the preaching of missions, Lockhart was entrusted with the pastoral charge of Shepshed on 5 June 1847. He was still occasionally employed for mission work and in 1850 was definitely appointed for this duty. After some years' successful preaching in various parts of England and Ireland, he was compelled, owing to ill-health, to spend the winter of 1853 at Rome. On his return journey he paid a memorable visit to Antonio Rosmini-Serbati, at Stresa.