Background <p>Polycystic ovary syndrome (PCOS) is the most common endocrine metabolic disorder among women of reproductive age, and its specific aetiology remains unclear, and clinical diagnosis presents challenges.</p> Aims <p>To investigate the diagnostic value of miR-935 in PCOS and its effects on ovarian granulosa cell (KGN) proliferation and apoptosis.</p> Methods <p>This study included 103 patients with PCOS and 75 healthy individuals. The diagnostic value of miR-935 was evaluated using receiver operating characteristic (ROC) analysis. Cell proliferation and apoptosis in KGN cells were assessed using the CCK-8 assay and Annexin V-FITC/PI staining kits. Pearson or Spearman correlation analysis was used to analyse the correlation between two factors. Dual luciferase assay identified the relationship between miR-935 and STAT1.</p> Results <p>miR-935 was upregulated in PCOS patients’ serum and correlated with key endocrine markers, including FINS, FSH, LH, E2, P, T, AMH, and AFC. The ROC curve of miR-935 effectively distinguished healthy individuals from those with PCOS. Inhibiting miR-935 attenuated proliferation and promoted apoptosis in KGN cells, whereas overexpression of miR-935 produced the opposite effect. miR-935 negatively regulated STAT1, and its effects on KGN cell proliferation and apoptosis were reversed by STAT1 silencing.</p> Conclusions <p>miR-935 may serve as a diagnostic biomarker for PCOS and promotes proliferation and apoptosis in KGN cells by negatively regulating STAT1.</p>