Background: Women undergoing mastectomy may have postural asymmetries due to mutilation, culminating in changes in postural balance. Aim: This study aimed to evaluate the influence of the mastectomy in the postural control of women undergoing surgical treatment of breast cancer. Methods: We evaluated 40 volunteers divided into two groups: women undergoing mastectomy (MG) with a mean age of 51.45 (SD 6.49) years old and mean BMI of 30.71 (SD 5.21) kg/m², and a control group of women without the disease (CG) with a mean age of 50.50 (SD 7.85) years old and mean BMI of 30.50 (SD 5.77). Static balance was assessed using the displacement of the center of pressure (COP), with voluntary bipedal support with eyes open and closed on a force platform. Statistical analysis was performed using the software SPSS 21.0 with a significance level of 5%. Results: The MG showed an increase in the displacement area along the x-axis (P = 0.003) and total displacement (P < 0.001) with eyes open (EO), and an increase in the x-axis (P = 0.002) and total displacement (P < 0.001) with eyes closed (EC). Velocity in the x-axis (P < 0.001), y-axis (P < 0.001) and total velocity (P < 0.001) was higher with EO than EC. A rise in velocity was also observed in the x- and y-axis, and in total velocity with EC, when compared with the CG (P < 0.001). Displacement was higher for all variables in both groups with EC (P < 0.001). Conclusions: Surgery for unilateral mastectomy may significantly alter postural control in women with breast cancer.