Stromal antigen 2 (STAG2) is an important member of cohesin, a conserved complex holding the sister chromatid together. Recent whole-genome sequencing studies have identified that genetic alterations of stag2 are common in bladder cancer (BC). The prognostic implications of STAG2 expression in BC remain unclear; we therefore analyzed its associations with the histopathological characteristics and clinical outcome in a Chinese population. We used immunohistochemistry assay to determine STAG2 protein expression in tumor tissues from 125 BC patients. STAG2 expression was analyzed according to clinicopathological features and patients' survival. Univariable and multivariable analyses were performed to identify predictors for recurrence-free survival (RFS) and cancer-specific survival (CSS). STAG2 expression was detected in 79.2 % of BC tissues, and 20.8 % of the tumor tissues had a complete loss of STAG2 protein expression. This STAG2-negative result was associated with a lower tumor histological grade with P = 0.009. The log-rank analysis revealed that the complete loss of STAG2 expression was associated with a lower risk of recurrence (P = 0.023) and a diminished risk of death (P = 0.034), especially in the subgroup of muscle-invasive BC (P = 0.043 for RFS and P = 0.087 for CSS). In multivariable Cox regression models, the loss of STAG2 expression remained a beneficial factor for RFS and CSS of BC patients. Univariate and multivariate analyses' results indicated that the complete loss of STAG2 expression was predictive for better RFS and CSS, suggesting its potential value as a prognostic biomarker.