In light of rapid rise in childhood obesity, there is a growing concern on the onset of multiple lifestyle behaviours during adolescence, a stage where establishment of lifelong health behaviours affects future health in adulthood. A cross-sectional study was conducted in two randomly selected government secondary schools in Selangor, Malaysia to determine multiple lifestyle factors associated with overweight and obesity among adolescents aged 13 to 16 years. A total of 513 adolescents (41% males and 59% females) with a mean age of 14.0±1.3 years participated in this study. They answered a self-administered questionnaire on socio-demographic background, eating behaviours, meal consumption pattern, physical activity and sleep quality. Weight, height and blood pressure were measured, while physical fitness was assessed using the modified Harvard-step test. Results showed that the prevalence of overweight and obesity was 33%, while prehypertension and hypertension rate were 19% and 12%, respectively. Unhealthy behaviours were prevalent in adolescents, in which 86.4% skipped at least one meal daily, 38.8% had low physical activity level, 63.9% had low physical fitness level, and 72.5% had poor sleep quality. After controlling for age, income level and parent’s years of education, greater BMI-for-age was predicted by higher restraint eating (β=0.191, p<0.001), emotional undereating (β=0.140, p=0.001), lower food responsiveness (β=-0.115, p=0.008), less frequent dinner intake (β=-0.104, p=0.014), poorer physical fitness level (β=-0.258, p<0.001) as well as shorter weekdays sleep duration (β=-0.117, p=0.017) (R2=0.193, F=10.287, p<0.001). These findings highlight the importance of targeting multiple modifiable lifestyle factors in reducing overweight and obesity among adolescents during the years of great opportunity for health.