Upon graduating, he joined France's Bureau of roads and bridges, taking up a position in Sour al-Ghozlane (then called Aumale) in Algeria.

Shortly thereafter they embarked upon an expedition to Susa, where Dieulafoy and his wife explored the remains of the palace first uncovered by William Loftus some thirty years previously.

That year he obtained a grant from the newly founded Department of Antiquities at the Louvre and from the Ministère de l'Instruction publique as well as logistical support from the French army and navy in order to fund further study.

It was Tholozan, then official physician to the Qajar court, who intervened on Dieulafoy's behalf with the Persian authorities to obtain permission to explore Susa further, with the proviso that the Tomb of Daniel not be disturbed.

Nonetheless, Dieulafoy's expedition succeeded in discovering numerous objects, most of which ended up in the Louvre Museum since the Persian government, uninterested in the largely brick and stone mortar fragments that were unearthed, waived its right to share in the discoveries.

He returned to the French civil service, taking a position in the administration of the national rail system and devoted himself to biblical studies.

He was elected to the Académie des Inscriptions et Belles-Lettres in 1895 and started to research the history of French architecture and the early sculpture of Spain and Portugal.

The fine quality of these images, many of sites that have subsequently been destroyed, damaged, or badly restored, means the work remains an invaluable scholarly resource.