Objective The aim of this study was to examine the effects of a 6-week community-based physical activity (PA) intervention on physical function-related risk factors for falls among 56 breast cancer survivors (BCS) who had completed treatments. Design This was a single-group longitudinal study. The multimodal PA intervention included aerobic, strengthening and balance components. Physical function outcomes based on the 4-meter walk, chair stand, one-leg stance, tandem walk, and dynamic muscular endurance tests were assessed at 6-week pre-intervention (T1), baseline (T2), and post-intervention (T3). T1-T2 and T2-T3 were the control and intervention periods, respectively. Results All outcomes, except the tandem walk test, significantly improved after the intervention period (p < 0.05), with no change detected after the control period (p > 0.05). Based on the falls risk criterion in the one-leg stance test, the proportion at risk for falls was significantly lower after the intervention period (p = 0.04), but not after the control period. Conclusions A community-based multimodal PA intervention for BCS may be efficacious in improving physical function-related risk factors for falls, and lowering the proportion of BCS at risk for falls based on specific physical function-related falls criteria. Further larger trials are needed to confirm these preliminary findings.