In his first Tour De France in 1909, he abandoned early due to wintery conditions during the month of July, but not before he managed a Stage 2 second place behind Tour winner Francois Faber. The following year he went head-to-head with Alcyon teammate Faber who led comfortably until colliding with a dog at the foot of the Pyrenees. Lapize finally won by just 4 points helped by a number of punctures to Faber's bike on the final stage from Caen to Paris. In a total of six starts in the Tour De France between 1909 and 1914, this victory was the only one he finished.
He is noted for looking at some Tour officials on the climb of the Col du Tourmalet in the 1910 Tour de France and yelling, "Vous êtes des assassins! Oui, des assassins!' (French for 'You are murderers! Yes, murderers!')" The stage in question was 326 kilometers in length, featured 7 brutal climbs, and was raced on unsealed roads with single-gear bicycles.
The First World War ended his cycling career. As a fighter pilot in the French army, Octave Lapize was shot down near Flirey, Meurthe-et-Moselle on 14 July 1917. Severely injured, he died in a hospital in Toul.