With a choice of subjects rooted in the Hague School paired with a style and use of colour associated with the Amsterdam Impressionists, Willem de Zwart is sometimes referred to as the 'Breitner of The Hague'. His landscapes, figural scenes and still lifes are rendered in deft, bold brushstrokes, thickly applied, sometimes straight from the tube, in vivid shades of lavish red, yellow and blue that imbue his paintings with brilliant life.

His work can be found at the Gemeentemuseum in The Hague, Museum Kröller-Müller in Otterlo and in other collections.