Aim Here, we aimed to compare the effect of a combination of body mass‐based resistance exercise and moderate‐intensity (55% peak oxygen uptake [ V˙O2peak]) walking or high‐intensity (75% V˙O2peak) walking on muscle size and V˙O2 peak in untrained older women. Methods A total of 12 untrained older women (mean age 60 ± 2 years) were randomly assigned to either a moderate‐intensity aerobic training group (n = 6) or high‐intensity aerobic training group (n = 6). Both groups carried out body‐mass based (lower body) resistance exercises (2 sets of 10 repetitions) on 3 days/week for 8 weeks. Between these exercises, the participants in the moderate‐intensity aerobic training group walked at a previously determined speed equivalent to 55% V˙O2peak, whereas those in the high‐intensity aerobic training group walked at a speed equivalent to 75% V˙O2peak. Results Muscle thickness of the anterior aspect of the thigh and maximal isokinetic knee extension strength significantly increased in both groups (P < 0.01); these relative changes were negatively correlated with the absolute muscle thickness of the anterior aspect of the thigh value and the relative value of maximal knee strength to body mass at pre‐intervention, respectively. A significant group × time interaction was noted for V˙O2peak (P < 0.05), which increased only in the high‐intensity aerobic training group. Conclusions Body mass‐based resistance training significantly induced muscle hypertrophy in untrained older women. In particular, lower muscle thickness before intervention was associated with greater training‐induced growth. Furthermore, V˙O2peak can be increased by combined circuit training involving low‐load resistance exercise and walking, particularly when a relatively high intensity of walking is maintained. Geriatr Gerontol Int 2017; 17: 779–784.