To investigate the effect of shoulder exercises during radiotherapy in relation to prevention of locoregional physical complications: limitation of range of motion (ROM) and functional capacity, arm circumference and scar tissue adhesion. Methods: Sixty-six women without shoulder ROM impairment following breast cancer surgery that included complete axillary dissection were allocated to one of two groups: 32 in the physical therapy group (PG) (52.7±10.2 years), who underwent an exercise program; and 34 in the control group (CG) (48±10.1 years). Shoulder ROM, upper-limb circumference and functional capacity and scar tissue adhesion were evaluated at the beginning and end of radiotherapy and six months after completing radiotherapy. Results: The PG showed improvements in flexion and abduction ROM between the first and third evaluations (flexion from 164.77°±8.9° to 167.98°±9.5° and abduction from 168.56°±10.0° to 175.62°±10.2°), which was not observed in the CG (flexion from 167.06±06° to 165.16°±9.2° and abduction from 169.71°±10.1° to 169.53°±12.8°). There was a statistically significant increase in ROM in the PG in relation to the CG (flexion, p=0.02; and abduction, p=0.004). The circumference and functional capacity were similar between the groups and the frequency of scar tissue adhesion in the CG was twice that observed in the PG (48% versus 24%, p=0.04). Conclusions: These results suggest that shoulder exercises favor maintenance of flexion and abduction ROM of the shoulder and minimize the incidence of scar tissue adhesion in women undergoing radiotherapy for breast cancer treatment.