Introduction: There is little published information exploring the perceptions and physical activity patterns among undergraduate medical students in our country. So this study was conducted with the following objectives: 1. To assess the perceptions about knowledge regarding physical activities among undergraduate medical students; 2. To assess their self-reported physical activity practices. Materials and Methods:This cross sectional study was conducted in Kasturba Medical College, Mangalore from 12th to 30th April, 2012. A total number of 427 students were chosen at by using the formula for infinite population. Tools: 1. A semi-structured questionnaire to know perceptions, barriers, and practices about physical activity; 2. Physical activity was assessed using International Physical Activity Questionnaire (IPAQ). Analysis was done by using SPSS version 11. Significance of differences across various levels of physical activity between different age-groups and gender were made by chi square test. Results: 376 students participated. Majority of them had high physical activity (54.75%). Knowledge was poor about prevention of diabetes (68.9%), stroke (61.6%), and osteoporosis (33.8%). Majority (82.4%) of them perceived healthrelated benefits of physical activity as motivating factors rather than prevention of chronic noncommunicable diseases. Most of them (72.3%) have enrolled in life style modification activities like yoga, going to gymnasium, etc. Conclusion: Most of the students fall into moderate physical activity group. Health-related benefits were the driving force for doing physical activity.