Collagen is a naturally occurring polymer with unique triple helical structure, which is the main structural component of leather [1]. The thermal stability of leather has important implications for practical applications and is affected by many factors. In the present work, the effect of re-tanning and fat-liquoring, two important post-tanning operations [2], on thermal degradation behaviors, kinetics and mechanisms of chrome-tanned leather (CTL) was investigated by using thermogravimetry (TG) and TG-Fourier transform infrared (TG-FTIR). The activation energy (Ea) values for the thermal degradation of chrome-tanned, re-tanned and fat-liquored leathers at different conversions were calculated using modified Kissinger-Akahira-Sunose (MKAS) method [3]. It was found that the average value of Ea decreased after re-tanning and fat-liquoring operations. The thermal degradation mechanism was predicted and compared based on single-step and multi-step reaction models with the combination of isoconversional and master plots methods. The results suggested that a two-parallel-reaction model could match the An model better than single-step one. TG-FTIR results showed that CO2, H2O, NH3 and pyrrole were main evolved gaseous products during CTL thermal degradation and confirmed an enhancement of gas release after re-tanning and fat-liquoring operations.