In 1863, during his third year of medical school, Dieulafoy went to Paris to attend the clinical department of Professor Armand Trousseau.

Dieulafoy married his cousin Claire Bessaignet in 1872, however the couple remained childless their entire marriage.

[1] He perfected a pump-like device for use in thoracentesis, and extensively studied pleurisy and liver conditions including hydatid disease and epidemic hepatitis.

He declared: "Le traitement médical de l'appendicite aiguë n'existe pas (The medical treatment of acute appendicitis does not exist)".

In 1890, Dieulafoy, André Chantemesse and Georges-Fernand Widal described a pulmonary condition found in persons who habitually fed pigeons in the streets.