Background: Overweight and obesity rates among adolescents have increased substantially over the years. This study aimed to determine the body mass index (BMI) of students and parents and the relationship among media use, BMI, socio-demographic profiles, and snacking behaviour during television watching of secondary school students in Kuching South City. Methods: In accordance with the two-stage sampling method, a total of 316 adolescents aged 13–17 years from 7 secondary schools participated. Data were collected using questionnaire and anthropometric measurement. Independent t test, one-way ANOVA, Mann–Whitney U test, and chisquare test were performed. Results: The mean BMI was 20.56 kg/m2 (SD 4.33) for boys and 20.15 kg/m2 (SD 3.91) for girls. No significant difference in terms of z score for BMI-for-age or socio-demographic factors was found. The mean duration of time devoted to media use was 4.69 hours (SD 2.93) on weekdays and 5.69 hours (SD 2.87) on weekends. Boys were found to spend more hours on media use than did the girls (t = 4.293, P < 0.01). Respondents were reported to consume more cereal compared with soft drinks and junk foods. Respondents whose fathers worked in the private sector devoted the fewest hours to media use, whereas those with self-employed fathers devoted the most time to media use. Respondents with mothers who were employed spent more time on media use than did respondents whose mothers were housewives (F = 4.067, P < 0.01). No significant difference was found between BMI and media time or snacking habits. Conclusion: This finding indicated that media time has no effect on body weight, because respondents were found to have normal weight and to consume less unhealthy food.