He worked under zoologist Léon Vaillant (chair of reptiles and fishes) at the Muséum national d'histoire naturelle.
He obtained doctorates in medicine (1899) and science (1904), and in 1908 was named as an assistant director.
[1] After many missions abroad, he became sub-director of the museum in 1937, and replaced Louis Roule (1861–1942) as the chairperson of herpetology and ichthyology.
He named a number of fishes from the family Cichlidae, such as the genera Astatoreochromis, Astatotilapia, Boulengerochromis, Lepidiolamprologus, Nanochromis and Ophthalmotilapia.
Pellegrin fought with the French Resistance during World War II.