Urinary bladder cancer (BC) is the fifth most common cancer worldwide with alarming mortality. Shortcomings of urine cytology and cystoscopy and sparse improvements in the survival rate prompt us to evolve surrogate serum based protein biomarkers to identify BC at an early stage. Previously, we showed that aberrant expression of S100A4, S100A8, S100A9, carbonic anhydrase I (CA I) and Annexin V proteins in pre-operative BC serum compared to healthy controls (HC) (Clin Chim Acta, 2014; 36: 97–103). Here we further evaluate and validate these findings with follow-up post-operative BC patients. This study was conducted on 160 sera samples comprising healthy controls (HC, n = 52), pre-operative (n = 55) and post-operative (n = 53) BC patients. Enzyme-linked immunosorbent assay (ELISA) was used to appraise the aberrantly expressed proteins. ELISA results revealed that the expression levels of S100A8, S100A9, S100A4, and CA I were gradually and significantly reduced; concomitantly, Annexin V was progressively and significantly increased in post-operative compared to pre-operative BC sera samples. Serum protein biomarkers appear to be an encouraging and least-invasive approach for BC identification and prognosticating patient outcomes.