A head-and-shoulders portrait of the sitter, facing to the right. He wears a large white collar, a sword belt over his right shoulder and red cloth trimmed with gold over his left. With shoulder length brown hair, he looks out of the image but does not engage the eye of the viewer.

Kortenaer was killed when third-in-command of the Dutch fleet at the Battle of Lowestoft, 1665. This was the first fleet action of the Second Dutch War and the only one in the first year. Both sides had over a hundred sail and the action began at 3.30 a.m. and continued until 7.00 p.m., by which time the Dutch were in flight, leaving seventeen ships sunk or captured. Kortenaer was admiral of the third of the seven squadrons, on board the 'Groot Hollandia', 66 guns.

The artist adopted the free and spontaneous style of Frans Hals in his portraiture. He took over from Rembrandt as the most popular portrait painter in Amsterdam. His interpretations were more flattering in their likenesses of the city bourgeoisie, and of state officials such as Kortenaer, than those of Rembrandt. This small painting is believed to be after the three-quarter-length portrait by the same artist.