Generally, exercise frequencies of more than or equal to 2 or 3 days a week for aerobic and strength exercises are recommended, respectively. However, such recommendations are difficult to maintain. Therefore, this study was conducted to observe the effects of once-a-week circuit training program on body composition and physical fitness. 22 healthy sedentary collegiate females in their twenties participated in 12-week circuit training program. Body composition and physical fitness were assessed before and after the training program. Body composition was assessed with the Bioelectrical impedance method. Physical fitness factors of vertical jump, static squat, knee push-up plus, and one-legged stance with eyes closed were also assessed. The total exercise program with duration of 80 minutes included machine weight, prep, and body weight, warm-up, and cool-down exercises with 1-minute resting period between each exercise. The results obtained at the baseline and after the program were compared via the paired t-test. As results, mean body weight and BMI (body mass index) were significantly reduced from 55.7±5.8 to 54.6±6.1kg (1.9%) and 21.4±1.4 to 21.0±1.5kg (-1.9%), respectively. Fat mass changed from 21.4±1.4kg and 20.6±2.2kg (-3.9%), respectively, without significance. All of the physical fitness factors, grip strength, vertical jump, knee push-up, static squat, and one-legged stance with eyes closed, significantly increased from 26.6±2.6 to 28.6±4.3kg (7.4%), 32.7±6.4cm to 38.9±7.3cm (18.9%), 25.5±6.6 to 47.9±12.0 (88.2%), 54.8±13.2 to 87.1±11.7 seconds (59.1%), and 43.0±17.4 to 58.8±20.4 seconds (36.6%), respectively. In conclusion, once-a-week high intensity circuit training may be beneficial for improving body composition and physical fitness factors of muscle strength and endurance.