Abernethy was an assistant surgeon in 1787 when he began to give public lectures, which soon attracted large crowds. Percy Bysshe Shelley briefly attended a number of Abernethy's anatomical lectures in 1811. In 1813 he was appointed surgeon to Christ's Hospital, and in the following year became Professor of Anatomy and Surgery at the College of Surgeons. In 1815 he received his final appointment as full surgeon to St. Bartholomew's, which he retained until two years before his death. His celebrity, owing to both his popular lectures and his eccentricity, gave him a considerable practice throughout his career.