Background: One in every ten deaths globally is reported by physical inactivity related risks. Adolescents constitute 18% of the total population, due to physical inactivity they are more at risk of noncommunicable diseases. This study aims to find the level, stages of behaviour changes, associated barriers related to physical activity among adolescents. Methods: Quantitative, cross-sectional study was done at Tagore College based on Multi-stage cluster sampling. 920 adolescents in the age group of 18-19 years were included in the study. Global Physical Activity Questionnaire (GPAQ) and Trans theoretic models were used to assess the level of physical activity and stages of behaviour change related to physical activity. In addition, barriers to participating in physical activity were also elicited. Result: About one-fifth of the subjects (20.4%) were physically inactive. It was found that they are in pre-contemplation and contemplation stages (14.7%) of behaviour change related to physical activity. Compared to females, males have a higher chance to do physical activity and was statistically significant (p<0.001). The major barriers to physical activity were personal barriers like lack of time and having multiple tasks. Healthy practices in a family also found to have a significant association with increased physical activity. (p<0.001). Conclusion: Many barriers were reported that prevent adolescents from taking up sufficient physical activity. Therefore, attempt should be taken to emphasize the importance of physical activity among family members, individuals, and the peer friends at the community level. Primordial prevention in the vital emergence of risk factors for NCDs like sufficient physical activity is vital for reducing burden of chronic diseases in our country.