Van Delen's painting was entirely devoted to architectural subjects. His early works, particularly the views of the palaces, borrow heavily from the work of Hans and Paul Vredeman de Vries. The buildings appear more heavily constructed than the Vredeman de Vries prototypes and are decorated in a more modern manner, based on that found in such Italian prints as Bernadino Radi's sepulchre designs and Michelangelo's porch of the Campidoglio reproduced in the Vignola editions. After 1630 his style became more exuberant, with his palette brighter and lighter, and his work became dominated by palace exteriors. His predominant use of pink, black and white marble in his architecture, and an excess of sculpture, clearly show the influence of the Antwerp Baroque style.