Blackburne was appointed Lord Chancellor of Ireland in February 1852, but was replaced in October. After a break of four years, he became a Lord Justice of Appeal. In 1858 'he was invited by Lord Derby again to become lord chancellor, but he declined on account of his advanced age and failing health. He changed his mind, however, and decided to accept Derby's offer but was told that the position had been offered to and accepted by Joseph Napier.' He was bitterly disappointed, referring to the decision as "a harsh and cruel blow". In 1866, he began a second term as Lord Chancellor, which ended with his death in the next year. Blackburne prosecuted Daniel O'Connell and presided at the trial of William Smith O'Brien. From 1851, he was vice-chancellor of the University of Dublin. A devoted member of the Church of Ireland, he opposed any measure hostile to its interests, arguing that an attack on the Church. was an attack on the Union itself. In 1809, he married Jane, daughter of William Martley of Ballyfallen, Co. Meath and his wife Elizabeth, daughter of Richard Rothwell of Berford, Co. Meath. They were the parents of three sons and three daughters. Blackburne bought Rathfarnham Castle in 1852, where his family continued to reside for three generations.