This study of the sustainable behaviour of engineering students in three technical universities in Malaysia was carried out to determine two things. First, the study seeks to find students' perception of their level of sustainable behaviour related to the environment. Second, to identify the relationship and the influence of demographic factors, internal and external, on sustainable behaviour. Three hundred and seventy-nine respondents were randomly selected from three technical universities, University Tun Hussein Onn Malaysia (UTHM), University Malaysia Pahang (UMP) and University Malaysia Perlis (UniMAP). The research method used quantitative survey using questionnaires as the research instrument. The questionnaire was divided into three parts. Part A was on demography of the students, while Part B focussed on sustainable behaviour and Part C was on the factors of sustainable behaviour. The analysis used a test score min, Pearson correlation and linear regression obtained using the Statistical Package for the Social Sciences (SPSS) software. The analysis showed that the perception of the level of sustainable behaviour of the students was high and positive. The findings also showed a positive and significant relationship between sustainable behaviour and internal factors such as knowledge and internal motivation (r=0.665, r=0.495)and between sustainable behaviour and external factors, social influence social and external motivation (r=0.593, r=0.299). It is found that there is high relationships between knowledge, social influence, and motivation with sustainable behaviour. However, there is no relationship between demographic factors and sustainable behaviour.