Female medical students tend to have low physical activity levels (PAL) accompanied by a poor sleep quality. This condition could disrupt muscle protein metabolism, resulting in decreased muscle mass at a young age. This study aimed to determine the association between physical activity and sleep quality with muscle mass in female medical students. A cross-sectional study design was conducted on 60 female students according to the criteria selected using stratified random sampling. The study instruments were Tanita Medical Body Composition Analyzer (MC-980MA Plus), Global Physical Activity Questionnaire (GPAQ), and Pittsburgh Sleep Quality Index (PSQI). Study results found that 34 (56,7%) subjects, 23 (38,3%) subjects, and 3 (5%) subjects had low, normal, and high muscle mass respectively. Physical activity levels (PAL) of 25 (41,7%) subjects were low, 30 (50%) subjects were moderate, and 5 (8,3%) subjects were high. A number of 55 (88,3%) subjects had a poor sleep quality, while the other 7 (11,7%) subjects had a good sleep quality. Multiple regression logistic test showed that PAL had more effects on muscle mass (p = 0,000; OR = 14,056, CI = 3,488-56,637) compared to sleep quality (p = 0,104; OR = 7,680, CI = 0,657-89,726). Therefore, young adults need to exercise regularly and perform sleep hygiene to maintain their muscle mass.