On 7 May, in Kassel, and then, again, on 1 June 1818 at Buckingham Palace, Princess Augusta married her second cousin, the Duke of Cambridge, when she was 20 and he 44. Upon their marriage, Augusta gained the style HRHThe Duchess of Cambridge. The Duke and Duchess of Cambridge had three children.
From 1818 until the accession of Queen Victoria, and the separation of the British and Hanoverian crowns in 1837, the Duchess of Cambridge lived in Hanover, where the Duke served as viceroy on behalf of his brothers, George IV and William IV. In 1827 Augusta allowed that a new village, founded on 3 May 1827 and to be settled in the course of the cultivation and colonisation of the moorlands in the south of Bremervörde, would bear her name. On 19 June the administration of the Hanoveran High-Bailiwick of Stade informed the villagers that she had approved the chosen name Augustendorf for their municipality (since 1974 it is a component locality of Gnarrenburg). The Duke and Duchess of Cambridge returned to Great Britain, where they lived at Cambridge Cottage, Kew, and later at St. James's Palace. The Duchess of Cambridge survived her husband by thirty-nine years, dying at the age of ninety-one.