He was also active in overseas trade between the East Indies and Europe as a partner in the firm Duntzfelt, Bloom og Kierulff.

[1] Duntzfelt visited Denmark in 1788 and married the daughter of the wealthy merchant Frédéric de Coninck on the Dronninggård estate in July 1790.

He became a managing partner in the firm Pingel, Meyer, Prætorius & Co. which had been initiated by his father-in-law in 1787 as a replacement for the Baltic African Company.

He was granted citizenship (borgerskab) as a merchant (grosserer) in 1795 and, in 1796, Duntzfelt and de Coninck decided to dissolve the consortium and transfer the activities to their personal firms.

He had profited immensely from Denmark's neutrality but many of his ships were still captured by English and French privateers and subsequently confiscated by court order.