Purpose <p>The aim of this study was to examine the short-term effects of early rehabilitation on physical and psychosocial functions in individuals undergoing breast cancer surgery.</p> Methods <p>Sixty-three female patients with breast cancer who were scheduled for surgery were randomly divided into three groups using the closed envelope method. Participants in Group 1 (G1) received preoperative patient education, exercised under the supervision of a physiotherapist during postoperative hospitalization, received a patient information brochure, and were followed up for 3&#xa0;months after surgery with telephone calls at 2-week intervals. Participants in Group 2 (G2) received preoperative patient information and a patient information brochure. Participants in Group 3 (G3) received only preoperative patient information. Upper extremity circumference measurements, tissue dielectric constant measurements, shoulder Function, quality of life, and fatigue level assessments were repeated preoperatively, at postoperative discharge, and 3&#xa0;months after surgery.</p> Results <p>The limb volumes of all the groups increased over time (<i>p</i> &lt; 0.05; except the volume of the unaffected limb in G2). The volume difference between the extremities increased over time only in G2 (<i>p</i> &lt; 0.05). The subdermal fluid ratios of all the groups increased after surgery but decreased after 3&#xa0;months. The modified Constant–Murley score, which reflects shoulder Function, decreased in all groups after surgery and was similar to the baseline value after 3&#xa0;months, except G3, in which the score was significantly lower than the baseline value (<i>p</i> &lt; 0.05).</p> Conclusions <p>The results of this study revealed that the physical and psychosocial functions of individuals deteriorate after breast cancer surgery, but early physiotherapist follow-up is effective in maintaining these functions and preventing breast cancer-related lymphedema.</p> Trial registration <p>NCT04979715 (27/07/2021)</p>