A study on the self-ignition of a propylene–oxygen–argon stoichiometric mixture with a volumetric argon content of 95% was carried out. The experiments were performed on a shock tube, which is part of the “Shock Tube” experimental complex of the Institute of Mechanics of Moscow State University, in conditions behind the reflected shock wave. The time dependences of signals from a piezoelectric pressure sensor, a thermoelectric detector and an optical section configured to record the radiation of electronically excited radicals OH^• (l = 302 nm), CH^• (l = 427 nm, and molecular carbon C₂^• (l = 553 nm) were analyzed. The ignition delay times τ_ign were measured in the temperature range T = 1200–2460 K and pressures p = 4.5–25 atm. The data obtained are compared with the results of other authors.