He negotiated a treaty with the Emperor of Vietnam that opened up the country to French commerce and ceded territory in the south to France.

[1] As governor of Réunion he was always helpful to scientific researchers, and in return the Madagascan fruit bat (Eidolon dupreanum) was named in his honour.

[2] He established new schools including the Collège de Stagiaires, in which Annamese officials were trained for the French administration.

Dupré ignored government instructions and dispatched Francis Garnier with a naval force to Hanoi, where it captured the Imperial Citadel of Thăng Long.

[8] He seems to have given Garnier the mandate of attempting to establish a colonial base in Tonkin, but his written orders did not include instructions to this effect since that would have been against French official policy.

[5] In 1874 Tự Đức ratified the treaty, under which the French could trade with Haiphong, Hanoi and Qui Nhơn, a step towards annexation of the whole of Vietnam ten years later.

[3][10] The treaty ceded the southern provinces of Vĩnh Long, Châu Đốc and Hà Tiên to the French.