The study aims to examine Malaysian and Indonesian undergraduate students’ sustainability knowledge and sustainable attitudes and the impact on their sustainability intention and sustainable behaviour. An online survey was conducted using 953 respondents. The SmartPLS (Partial Least Squares) analysis demonstrated that sustainability knowledge and sustainable attitude significantly impact the students’ sustainability intention. Nevertheless, the effect of sustainability knowledge was less than the sustainable attitude. The results confirmed that sustainability intention is important to influence sustainable behaviour among university students. Interestingly, Malaysian undergraduate students recorded higher effect levels of sustainability knowledge and attitude on sustainable intention and sustainability intention on sustainable behaviour compared to Indonesian students.