He exhibited frequently at the Royal Academy and the British Institution, and about 1815 was invited to London to paint a number of portraits, including those of the dean of Canterbury and Benjamin West.

In 1820, in spite of much opposition from the Royal Institution, the Scottish Academy was founded, and Watson, who had been president of the previous society, was elected to the same office in the new one, the ultimate success of which was largely due to his tact and ability.

It is said that he long maintained an honourable rivalry with Henry Raeburn but, although his grasp of character was firm, his executive power considerable, and his work belonged to a fine convention, his portraiture lacks the qualities which give that of his fellow artist enduring interest.

Returning to Edinburgh, he made a good connection as a portrait-painter, became one of the founders of the Scottish Academy, and for nearly 50years exhibited with unfailing regularity.

He was a devoted student of natural history, particularly ornithology, and formed an extensive collection of specimens, which he bequeathed the University of Edinburgh.