On leaving the service Fullarton entered the house of Alexander & Co., bankers of Calcutta, as a partner, acquired a fortune in a few years, and returned to England to live.
Meantime he had travelled widely over India, and about 1820 made a pioneering tour through the British Empire in the east.
The reform crisis led him to contribute articles to the Quarterly Review in defence of the Tory party, and he is said to have been one of the founders of the Carlton Club.
During these years he made extensive tours through Great Britain and the continent in a coach fitted up with a library and other luxuries.
Fullarton was a fellow of the Royal Asiatic Society, and took great interest in art, literature, and the drama.