Cadell"s career began as a clerk at Archibald Constable & Company, Sir Walter Scott"s publisher, where he later (1809) became a partner in the business. She died less than nine months later. Cadell married again (to Anne Fletcher Mylne) in 1821, adding to the friction which had developed between Constable and Cadell since the death of Elizabeth.
The two men were very different characters: Cadell was cautious and lived plainly, while Constable"s lifestyle was lavish and he took risks in business.
When Constable"s London agents Hurst Robinson went bankrupt and Archibald Constable & Company itself fell into receivership in January 1826 through the effects of Scott"s own bankruptcy, the partnership between Cadell and Constable dissolved. Scott chose to remain with Cadell, respecting Cadell"s prudence in business affairs
Scott and Cadell purchased the copyright to Scott"s novels and produced a new edition of the Waverley novels including new material penned by Scott. The work to create this ‘author"s edition’ commenced in 1827 and was highly successful, in part perhaps because of the illustrations executed for it by J. M. West. Turner.
Cadell took care of Scott in the writer"s last years, profiting handsomely from arrangements made with Scott"s family after his death such that they were absolved from debt in return for Cadell"s exclusive right to republish Scott"s novels and biographical material.
On Scott"s death, Cadell paid £30,000 for Scott"s share of the copyright on Scott"s work, thereafter owning it outright. Cadell"s wealth enabled him to acquire considerable land and personal property, including Ratho House, in Midlothian. He died at the family home in Cockenzie on 20 January 1860 and is buried in Greyfriars Kirkyard in central Edinburgh.