This study aimed to examine the relationship between healthy behaviour, self-efficacy, optimism, and subjective well-being, and to explore healthy behaviour predictors. The sample included (370) Lebanese students from Beirut Arab University, aged between 17 and 22 years. The results showed that women had a significantly higher mean scores than men in healthy behavior, while men had a higher mean scores than women in self-rating of both mental health and happiness. All correlation coefficients among the study scales were statistically significant and positive for both sexes. The principal components analysis, followed by the Varimax orthogonal rotation, extracted two factors namely "subjective well-being and optimism", and "self-efficacy and healthy behavior" in men, and "subjective well-being", "self-efficacy, optimism and healthy behavior" in women. Using regression analysis, the healthy behavior predictors were as follows: optimism, self-efficacy, and physical health in men as well as self-efficacy, and physical health in women. The present study, thus, indicated the significant relationship between healthy behavior, self-efficacy, and optimism, which are considered predictors of healthy behavior.