Background: Smoking among university students is a social and public health problem worldwide. There is a high prevalence of smoking in Saudi Arabia. Aims: To investigate the factors associated with the onset and cessation of smoking behaviour among university students in Saudi Arabia, and establish what contributes to changes of students' smoking behaviour. Methods: A sample of 340 students from a national university in Saudi Arabia was randomly recruited and surveyed twice at a 5-month interval. Multiple ordinal logistic regression was run to compare changes in social, psychological and political factors and their impact on students' smoking behaviour. Results: We found that beliefs supporting nonsmoking (e.g., religious prohibition of smoking) correlated with changes in smoking behaviour among university students [adjusted odds ratio (AOR) = 1.89, 95% confidence interval (CI) = 1.23-2.91]. There was a significant positive correlation between government policy and changes in male university students' smoking behaviour (AOR = 0.46, 95% CI = 0.29-0.072). The psychological effect of smoking, such as releasing psychological pressures, was also correlated with changes in smoking behaviour (AOR = 0.31, 95% CI = 0.21-0.47). Conclusions: Our study suggests that the government can play a significant role in curbing smoking by strengthening beliefs promoting antismoking among university students, by developing corresponding policies against smoking, and by providing psychological consultation for them.