The accelerated warming over the Tibetan Plateau relative to global means has attracted considerable attention from the scientific community. Nevertheless, the timescale, seasonality and dominant causes of the Tibetan warming amplification have not been discussed. The seasonality of the Tibetan amplification effect at different timescales was revealed in this study. Based on the optimal fingerprinting attribution method, an attribution study of the Tibetan warming amplification was also conducted after selecting the outperforming model simulations in the Coupled Model Intercomparison Project (CMIP6). Results showed that Tibetan warming amplification manifested in the mid-1970s. The annual amplification during 1961–2018 was 0.13 °C per decade. The warming amplification in spring started later than all the other seasons, and the strongest warming amplification occurred in winter. The change in Tibetan warming amplification also displayed distinct decadal differences at time scales shorter than 30 years. The updated models perform better in simulating the surface air temperature change on the global land scale whilst underestimating the warming over the Tibetan Plateau region, which causes a weak amplification in the model simulation. Overall, the largest deviation comes from winter. The attribution result reveals that the stronger warming response to human influence on the Tibetan Plateau than the global land is the direct cause of the Tibetan warming amplification. This finding implies the important role of local climate feedback over the Tibetan Plateau.