Quénisset was born on 8 August 1872 in Paris, the son of Gatien Jules Quénisset, an assistant director of the Administration des Monnaies et Médailles in Paris, and Juliette Antonia Mallard, a dressmaker.

[1][2] He became a member of the Société astronomique de France in 1890, after becoming interested in astronomy by reading Camille Flammarion's books.

[4] Quénisset worked as an observer at Flammarion's observatory in Juvisy-sur-Orge from 1891 to 1893, during which time he discovered a comet.

He was forced to abandon astronomy for a dozen years while he performed his military service, but then returned to Juvisy in 1906 to resume his post at the observatory (he succeeded Eugène Antoniadi, who had left Juvisy in 1902).

[5] Quénisset worked at the Juvisy observatory for the remainder of his career until 1947, when his health obliged him to quit.