His work focuses on the interaction between figures and their architectural settings. In genre pieces like "Scene in a Courtyard", he uses light to define the geometry of the space. De Jongh was adept at painting animals, especially horses and hunting dogs. His "De vossenjacht" demonstrates his ability to capture movement and the anatomy of hounds. He avoided heavy chiaroscuro, preferring a clearer distribution of light and colour that defined the textures of silk and stone.

Collectors value De Jongh for his technical precision and his ability to document Dutch life without sentimentality. His portraits of Jan van Nes and Aletta van Ravensberg offer a look at the fashions of the seventeenth century. The inclusion of X-radiograph prints of "Portrait of a Woman" reveals the hidden layers of his process, showing how he adjusted compositions for balance. These works provide a sense of order and historical detail for the home.