This study aimed to examine the effects of an 8-week physical activity program, which mainly comprised home-based bench-stepping exercise training at the intensity of lactate threshold (LT), on mental health (MH), health-related quality of life (HRQOL), and physical fitness in Japanese returnees from China. Thirty Japanese returnees (63 ± 9 y) participated in the exercise program. Another six subjects were enrolled as the control group. The subjects performed 212 ± 57 min of training, and their daily step counts were increased. Aerobic capacity (LT: 4.5 ± 0.8 vs. 5.5 ± 1.1 METs), lower limb strength (30-s chair stand test [CS-30]: 19.1 ± 5.5 vs. 21.3 ± 5.1 times), and sit-and-reach flexibility (sitting-posture body anteflexion: 36.1 ± 9.4 vs. 39.0 ± 8.4 cm) were significantly increased after the intervention compared with before the intervention. Furthermore, MH, as assessed by the total score of the GHQ-28 (3.4 ± 4.4 vs. 0.3 ± 0.8 points), and the mental component score (MCS) of HRQOL, as evaluated by the SF-36v2 (55.1 ± 11.4 vs. 58.5 ± 10.0), were significantly changed in a positive manner. However, a two-way repeated measures ANOVA (group × period) showed significant interactions for LT and MCS (p<0.05), and a tendency for interactions of CS-30 (p=0.063) and the total score of the GHQ-28 (p=0.098). These results indicate that this bench-stepping exercise program could become a useful health support program for improving physical fitness, as well as MH and HRQOL, in Japanese returnees.