John Hancock was the son of James Hancock, a cabinetmaker, and Betty Hancock (nee Coleman). He was a member of the Hancock family of Marlborough, England. The Hancocks were a significant British family in the eighteenth and nineteenth centuries, known for their contributions to science, art, and industry.

John Hancock is best known for working alongside his older brother Thomas Hancock at the family coach-making business, ‘Hancock and Co., Patent whalebone Coach-makers’. They inveted the Pilentum, or lady's accelerator. In later life, he moved to Cornwall to work with Humphry Davy, a chemist, on developing a safety fuse for tin miners. After his death in 1835, his nine children returned to London to live in the care of his brother Thomas.