Introduction:The efficiency of the T1 sub-staging system on categorizing bladder cancer (BC) patients into subgroups with different clinical outcomes was unclear. We summarized relevant evidences, including recurrence-free survival (RFS), progression-free survival (PFS), and cancer-specific survival (CSS), to analyze the prognostic significance of T1 sub-stage.Methods:Systematic literature searches of MEDLINE, EMBASE, and the Cochrane Library were performed. We pooled data on recurrence, progression, and CSS from 35 studies.Results:The pooled hazard ratios (HRs) and 95% confidence intervals (CIs) indicated the difference in RFS between T1a sub-stage and T1b sub-stage (HR 1.28, 95% CI 1.14-1.43,p< 0.001). The significant difference was observed in PFS between the 2 arms (HR 2.18, 95% CI 1.95-2.44,p< 0.001). Worse CSS was found in T1b patients than in T1a patients (HR 1.36, 95% CI 1.21-1.54,p< 0.001).Conclusions:T1 sub-staging system based on the invasion depth into muscularis mucosae can be a significant prognostic factor for RFS, PFS, and CSS of patients with T1 BC. Urologists and pathologists are encouraged to work together to give a precise sub-stage classification of T1 BC, and T1 sub-staging system should be a routine part of any histopathological report when possible. Different treatment strategies need to be developed for both T1a BC and T1b BC.