Purpose To investigate the incidence of scapular dyskinesis (SD) in patients with rotator cuff tears using pre- and postoperative 3D computed tomography, analyze the changes in scapular kinematics that occur after arthroscopic rotator cuff repair, and identify the contributing clinical factors. Methods Thirty-five patients (mean age, 62.5 ± 8.4 years) were included. Four scapular angles (upward rotation, internal rotation, protraction, and posterior tilt) were measured. The patients were categorized into three pre-existing SD types according to the difference in measured scapular angles between the affected and unaffected sides (type 1 SD, posterior tilt angle difference <  − 5°; type 2 SD, internal rotation angle difference > 5°; and type 3 SD, upward rotation angle difference > 5°). The prevalence, factors influencing SD, and outcomes were compared between the improved and sustained SD groups. Results Twenty three of the 35 patients (65.7%) with rotator cuff tears had SD (type 1, 11; type 2, six; type 3, six). Of the 23 preoperative SD patients, 12 (52.1%) showed improved SD postoperatively. Most of the patients with improved SD (9/12) had type 1 SD ( p  = 0.021) and a significantly improved posterior tilt angle ( p  = 0.043). The improvement in SD was correlated with a higher range of motion of forward flexion and higher Constant scores (all p  < 0.05). No healing failure occurred in the improved SD group ( p  = 0.037). Conclusion The prevalence of SD was high in patients with degenerative rotator cuff tears. More than half of the SD cases, especially type 1 SD, improved postoperatively. SD recovery correlated with better function and successful rotator cuff healing. Level of evidence IV.