In 1874, Hancock published his Catalogue of the Birds of Northumberland and Durham.
Hancock edited Thomas Bewick's 1847 edition of Birds. In 1868 he planned a layout for NewcastleTown Moor, which was only partly realised. In 1875 he was asked to prepare a plan for Saltwell Park, but declined due to pressure of work.
John Hancock was brother to the naturalist Albany Hancock. The brothers lived with their sister, Mary Jane, at 4 St. Mary’s Terrace, Newcastle, now part of a listed terrace at 14-20 Great North Road.
The Hancock Museum in Newcastle upon Tyne is named after the Hancock brothers, both of whom took an instrumental part in getting the museum built. The museum contains many specimens from their collections.