Lockwood was called to the bar at Lincoln's Inn in 1872, and joined the old midland circuit, afterwards going to the north-eastern, making in his first year 120 guineas and in the next 265 guineas. From that time he had a career of uninterrupted success, a high profile brief being the defence of the murderer Charles Peace in 1879. ... He was made a Queen's Counsel in 1882 and in 1884 he was made recorder of Sheffield.

In May 1895 Lockwood was lead counsel for the prosecution in Regina v. Oscar Wilde. The Liberal government seemed determined to get a successful prosecution. Edward Carson, who had successfully defended the Marquess of Queensbury against Wilde's misguided criminal libel, approached Frank Lockwood and asked "Can we not let up on the fellow now?". Lockwood answered that he would like to do so, but feared that the case had become too politicised to be dropped.