Willem van Aelst painted his first paintings in his native Delfl with his uncle, Evert van Aelst. Recorded as becoming a master of the Guild of Saint Luke at Delft on 9 November 1643,
Van Aelst traveled to France in 1645.In Paris he could have met Willem Kalf, the other leading Dutch still life painting master of the second half of the seventeenth century, whom Van Aelst would reencounter during his Amsterdam period.Van Aelst spent the years 1649 to 1656 painting in Florence and Rome. As court painter to the grandduke of Tuscany, Ferdinand 11 de Medici, Van Aelst was in Florence at the same time as his compatriot Otto Marseus van Schriek.A certain stylistic indebtedness to this still life painter has been noted in Van Aelst"s own composition paintings.
Like other northern artists resident in Rome, Van Aelst joined the Bentveughels, a fraternitylike society, well known for its high-spirited antics.We deduce from the signature of a game piece dated 1658 (Amsterdam, Rijksmuseum) that Van Aelst was known by the Bent nickname "Scarecrow." He returned to Delft in 1656 and by 1657 had settled permanently in Amsterdam.There he remained active in painting until at least 1683, the year of his last dated painting, producing an abundance of fruit, flower, and game pieces, as well as banquet still life paintings.