Objectives <p>This study aims to evaluate perceived social support (SS) in inpatients with mental disorders, its association with sociodemographic and clinical characteristics, and its impact on hospitalization patterns, highlighting the importance of evaluating and enhancing SS.</p> Methods <p>This hospital-based study, using a cross-sectional design, was conducted at the Psychiatric Clinic of University Hospital Larissa, Greece and included 280 consecutive admitted patients. SS was assessed with short form social support questionnaire SSQ-6, and sociodemographic and clinical characteristics were examined along with possibility of reentry during a 32-month period.</p> Results <p>Most respondents reported low SS levels, with significant differences in SS quantity across diagnostic categories. Sociodemographic factors, including age, work status, housing conditions, medical insurance and the number of cohabitants, were significantly associated with both SS quantity and satisfaction. Clinical factors, including diagnosis, illness duration and prior admissions also showed significant associations with both dimensions of SS. Multivariate analysis identified increasing age, urbanicity, homelessness, retirement, and unemployment as independent risk factors for lower SS quantity, while cohabitation and affective disorder diagnoses were protective factors. Regarding SS satisfaction, homelessness, retirement, and prolonged illness duration, emerged as risk factors, while medical adherence was protective. Notably, SS quantity was marginally negatively associated with involuntary type of admission. Low SS significantly increased the likelihood of readmission during the 32- month follow-up period.</p> Conclusions <p>The study highlights the critical role of assessing and enhancing SS in hospitalized patients with mental disorders. Sociodemographic and clinical factors significantly influence SS, with poor SS contributing to a higher risk of involuntary admission and increased readmission likelihood.</p>