After working at the British Museum for more than forty years, in 1909 Jenner and his wife Kitty retired to Hayle, his wife's home town, and in January 1912 he was elected as the Librarian of the Morrab Library, a post he held until 1927. He also served as President of both the Royal Cornwall Polytechnic Society and of the Royal Institution of Cornwall. Jenner had married Kitty Lee Rawlings, herself a Novelist and Writer on art, in 1877. He died on 8 May 1934 and is buried in St. Uny's Church, Lelant.