Waste sorting and recycling (WSAR) is a crucial issue for sustainable waste management. Growing up with new values, the younger generation has the responsibility to lead the society towards a sustainable future. The successful implementation of WSAR requires an in-depth understanding of the attitudes and obstacles of the youth participation. This study seeks to explore and compare the influencing factors of youth engagement in WSAR in Shenzhen, China and Turku, Finland by drawing on the theory of planned behaviour. Quantitative data was collected from 170 youth citizens in Shenzhen and 179 in Turku. Structural equation modelling results suggest that there is a clear consistency between the youth's intention and behaviour in both cities. Two reverse pyramids were constructed to prioritize the influencing factors based on their importance in the structural models. Subjective norms, knowledge and perceived behavioural control are key influencing factors in Shenzhen group while in Turku' s setting, compatibility acts as a top determinant whereas, subjective norms have the least influencing power. Results from Turku also reveal that lower compatibility does not necessarily hinder youth participation in WSAR practice. Several suggestions and implications on boosting youth participation in WSAR are drawn, based on these findings.