St Matthew, Apostle and Evangelist, is shown bust-length, with an open book and a pen in his right hand. At the lower left is the head of a putti or child angel, glancing out of the picture. The angel is St Matthew's traditional attribute, and he is sometimes shown dictating his Gospel to him. The style of this picture is close to Guercino's, who is known to have dealt with the subject in both drawings and paintings. Guercino's Account Book records paintings of St Matthew with the angel done in 1649 and 1653, and three drawings of St Matthew exist by Guercino, two in the Teylers Museum, Haarlem, and one at Windsor. Although there is no precise compositional correspondence, one of the Teylers Museum drawings (inv. no. H.17) provides the closest of surviving treatment of the subject to the present painting.

When it was in the collection of Consul Smith the painting had a pendant, which was presumably painted for it, of St John the Evangelist by Piazzetta. The work is no longer in the Royal Collection and cannot be traced today.