Adam (1732-94) was a leading Scottish exponent of the European Neoclassical movement and played a formative role in developing British architecture.
The “most ambitious and splendid surviving portrait” by Italian artist Antonio Zucchi has been jointly acquired by the Scottish National Portrait Gallery and the V&A following a £150,000 grant from charity the Art Fund.
It will go on show in Edinburgh on Friday before a stint in London later this year. The painting will then be shown on a seven-year rotation at each institution.
The work depicts Adam during his grand tour of Italy in 1763, before returning to London to work with his brother Robert.
Together with siblings John and William - sons of mason-architect William Adam - the family was regarded as Scotland’s foremost architects of the time.
Christopher Baker, director of European and Scottish Art and Portraiture at the National Galleries of Scotland, said: “James Adam’s portrait is a work of great swagger and refinement that demonstrates the confidence of the Adam family as seminal taste makers for 18th century Europe.
“It represents a splendid addition to the collection of the National Galleries of Scotland and we are immensely grateful to both the Victoria and Albert Museum and the Art Fund for making its joint purchase possible.”
Julius Bryant, keeper of word and image at the V&A, said the work is “ideal” for the Neoclassicism section of its British Galleries.
He said: “We are delighted it joins the V&A’s collection, together with two sculptures previously purchased with the National Galleries of Scotland.”