The Royal Scottish Academy started to acquire its collection in 1831 when it decreed that all members, on reaching the status of Academician, must deposit a Diploma Work. This should be a piece of work representative of their output in the discipline of painting, sculpture or architecture. Today the Diploma Collection contains 198 paintings, 36 sculpture and 48 architectural drawings or models by Academicians past and present.

Other facets of the RSA's art collections include : recent works by recipients of RSA scholarships (e.g. John Kinross Scholarship, Alastair Salvesen Trust); portraits of artists; copies of Old Masters; twentieth century material bought through specific funds; and mixed collections received through gifts and bequests. The largest single bequest was that of William Gillies. Received in 1973, it contains over a thousand paintings and drawings by this artist and many others by his friends and contemporaries.