Background <p>Shoulder problems are common in indoor competitive volleyball, but interpretation is complicated by inconsistent outcome definitions and methodological approaches. This systematic review synthesised the epidemiological burden and associated factors of shoulder problems by distinguishing shoulder pain, shoulder injury, shoulder-related functional disability, and specific shoulder pathology as separate outcomes.</p> Methods <p>Six databases were searched from inception to 21 March 2026. Eligible studies included indoor competitive volleyball players and reported a defined shoulder outcome or factors associated with that outcome. Risk of bias was assessed using Joanna Briggs Institute critical appraisal checklists. Because of substantial clinical and methodological heterogeneity, findings were synthesised narratively.</p> Results <p>Twenty-seven studies were included: 17 identified through database searching and 10 through backward citation searching. Burden estimates varied markedly according to outcome definition and recall or follow-up period. Shoulder pain prevalence ranged from 22% (point prevalence) to 38% (lifetime prevalence). Among female high-school players, the prevalence of non-traumatic shoulder pain during attacking or serving within the previous 24&#xa0;h was 54.2% (95% confidence interval, 40.6%–67.6%). In one prospective cohort of professional and masters-level athletes, the cumulative incidence of shoulder pain, shoulder injury, and shoulder-related functional disability was 52.6%, 38.9%, and 47.3%, respectively. Reported associated factors included previous shoulder pain or injury, scapular dyskinesis, strength imbalance, glenohumeral internal rotation deficit (GIRD), total range-of-motion (TROM) asymmetry, proprioception, dynamic stability, spike technique, playing position, training exposure, swing volume, thoracic posture, and core endurance. Most evidence was observational, heterogeneous, and at moderate-to-high risk of bias.</p> Conclusions <p>Shoulder problems in indoor competitive volleyball constitute heterogeneous outcomes whose reported burden depends strongly on case definition and measurement period. Separating pain, injury, functional disability, and pathology provides a clearer framework for interpretation. Associated factors should be regarded as candidate evidence signals rather than confirmed causal or independent prognostic factors. Future studies should use standardised outcome definitions, prospective designs, repeated symptom monitoring, and adequate control of confounding.</p> Trial registration <p>PROSPERO CRD420261345614.</p>