B ackgroundAcute Mountain Sickness (AMS) is a disorder that is often experienced by novice climbers at an altitude of more than 2,500 m. According to a journal released by Military Medical Research in 2019, Murdoch stated that the prevalence of Acute Mountain Sickness (AMS) was 88.6%. In Indonesia, there are only a few studies and researches discussing AMS among mountain climbers. A good level of physical activity can make it easier for us to make a mountain climbing trip. The purpose of this study was to assess the relationship between physical activity levels and Acute Mountain Sickness in Mountain Climbers.MethodsThe research was conducted during February – June 2021 in the Mapala community and respondents who have been climbing a mountain using a study design cross-sectional. Physical activity level was measured using the questionnaire GPAQ , and the Acute Mountain Sickness was measured using the questionnaire LLS. Data analysis was processed by the SPSS program using the Test Chi-Square with a significance level of p<0.05.ResultsRespondents were dominated by the age group from 19 to 39 years old. More than half 50% of the respondents belonged the category of respondents with moderate activity levels, followed by respondents with heavy physical activity, which is 40.7%. Of the total of respondents, 81,4% was experienced mild AMS with moderate physical activity levels. The results of the Chi-Square test show that there is a significant relationship between the level of physical activity and Acute Mountain Sickness in Mountain Climbers p=0.034ConclusionThere is a relationship between physical activity level with Acute Mountain Sickness In Mountain climbers.