BACKGROUND: This study identifies the association of internet engagement with weight-related parameters and academic performance among adolescents in Malaysia. METHODS: This is a cross-sectional study which collected primary data on academic performance and used secondary data from the second wave of the Malaysian Health and Adolescents Longitudinal Research Team (MyHeARTs) Study cohort. The participants comprised 720 students attending year three public secondary schools from the states of Selangor, Perak and Federal Territory of Kuala Lumpur in Malaysia. Sampling was done using a two-stage cluster sampling design. RESULTS: The prevalence of adolescents who engage on the Internet regularly was 85.3% (n=614). Among those who regularly engaged with the Internet, 53.9% (n=331) spent an average of ≥3 hours per day on the Internet while 46.1% (n=283) of them spent an average of < 3 hours per day on the Internet. Of the total participants, 57.6% (n=415) have a mobile phone or tablet with a data plan. Participants who regularly engaged on the internet were more likely to have better overall academic performance (OR=2.319, CI=1.118-4.810) than those who rarely engaged on the internet. However, participants who spent an average of ≥ 3 hours per day on the Internet had less likelihood of getting average in aggregate (overall academic performance) (OR=0.899, CI=0.811-0.996) compared to participants who spent an average of < 3 hours per day on the Internet. Participants who spent an average of ≥ 3 hours per day on the Internet had less likelihood of having excess body fat compared to the participants who spent < 3 hours daily on the Internet (OR=0.701, CI=0.493-0.997). CONCLUSION: Generally, time spent on the Internet is not associated with all weight-related parameters. It could be said that since majority of participants use mobile phone for internet engagement, thus it may not affect ones’ body composition. On the other hand, regular engagement on the internet was associated to better academic performance but it was found that spending more time on the internet resulted in poorer academic performances. As such, close monitoring, supervision, and guidance on Internet engagement among adolescents is crucial.