The aim of the study was to investigate the effects of a once weekly, online video bodyweight resistance exercise training on body mass, muscle strength, and quality of life in middle-aged men (age 40–50 years) during a 20-week coronavirus (COVID-19) pandemic period. The participants were 30 healthy men, and the intervention lasted from June 2021 to September 2021. The participants were randomly assigned in two groups: an exercise group (n = 15) and a congrol group (n = 15). The exercise group participated in a 45-minute program including warm-up, resistance exercise, and recovery once per week for 20 weeks. The participants in the exercise group showed significantly reduced body mass (76.08 ± 8.80 kg), body mass index (BMI, 25.23 ± 2.39 kg·m−2), body fat mass (14.93 ± 4.97 kg), body fat percentage (19.42 ± 5.31%), and waist circumference (91.40 ± 6.13 cm) and increased handgrip strength (right: 48.49 ± 6.98 kg and left: 44.44 ± 6.39 kg) and quality of life (total score: 25.80 ± 2.651). Meanwhile, the control group showed increased body mass (77.06 ± 9.04 kg) and body fat mass (19.10± 4.95 kg) and decreased quality of life (total score: 24.60 ± 3.180). The once-weekly online video bodyweight resistance exercise program could be beneficial for body mass, muscular strength, and quality of life among middle-aged men.