Photo–thermo catalysis, which integrates photocatalysis on semiconductors with thermocatalysis on supported nonplasmonic metals, has emerged as an attractive approach to improve catalytic performance. However, an understanding of the mechanisms in operation is missing from both the thermo‐ and photocatalytic perspectives. Deep insights into photo–thermo catalysis are achieved via the catalytic oxidation of propane (C3H8) over a Pt/TiO2‐WO3 catalyst that severely suffers from oxygen poisoning at high O2/C3H8 ratios. After introducing UV/Vis light, the reaction temperature required to achieve 70 % conversion of C3H8 lowers to a record‐breaking 90 °C from 324 °C and the apparent activation energy drops from 130 kJ mol−1 to 11 kJ mol−1. Furthermore, the reaction order of O2 is −1.4 in dark but reverses to 0.1 under light, thereby suppressing oxygen poisoning of the Pt catalyst. An underlying mechanism is proposed based on direct evidence of the in‐situ‐captured reaction intermediates. Photo–thermo catalytic oxidation of propane (C3H8) on Pt/TiO2‐WO3 catalyst proceeds with excellent activity at high O2/C3H8 ratios and low temperatures. An investigation of the apparent activation energy and reaction orders (relative to thermal catalysis) reveals that oxygen poisoning of the supported Pt catalyst is mitigated and performance is consequently enhanced.