Background and Objectives: To date, sparse evidence exists about the impact of inflammatory serum markers in predicting perioperative complications after radical cystectomy (RC) for bladder cancer (BC). Here, we evaluated the role of the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), systemic immune-inflammation index (SII), C-reactive protein (CRP), and plasma fibrinogen in predicting perioperative morbidity and unplanned 30-days readmission after RC for BC.Materials and methods: We relied on a collaborative database of 271 patients who underwent open RC for cT1-4a N0 M0 BC between January 2012 and December 2022. Univariable and multivariable binomial logistic regression analyses were performed to assess the odds ratio (OR) with 95% confidence intervals (CI) testing the ability of each serum marker to predict postoperative complications (any-grade and major complications), and 30-days unplanned readmission.Results: The median age at RC was 73 yr (IQR 67–79). A total of 182 (67.2%) patients were male and the median BMI was 25.2 (IQR 23.2–28.4). Overall, 172 (63.5%) patients had a Charlson Comorbidity Index (CCI) greater than 2 points and 98 (36.2%) were current smokers at the time of RC. Overall, 233 (86.0%) patients experienced at least one complication after RC. Of these, 171 (63.1%) patients had minor complications (Clavien–Dindo grade 1–2) while 100 (36.9%) experienced major complications (Clavien–Dindo grade ≥ 3). According to multivariable analysis, current smoking status, high plasma fibrinogen, and preoperative anemia were independently associated with major complications (OR 2.10, 95%CI 1.15–4.90,p= 0.02), (OR 1.51, 95%CI 1.26–1.98,p= 0.09), and (OR 1.35, 95%CI 1.17–2.57,p= 0.03), respectively. Overall, 56 (20.7%) patients experienced a 30-days unplanned readmission. According to univariable analysis, high preoperative CRP and hyperfibrinogenemia were significantly associated with an increased risk of unplanned readmission (OR 2.15, 95%CI 1.15–4.16,p= 0.02; OR 2.18, 95%CI 1.13–4.44,p= 0.02, respectively).Conclusions: In our study, the preoperative immune-inflammation signature described by NLR, PLR, LMR, SII, and CRP showed a low reliability in predicting perioperative course after RC. Preoperative anemia and hyperfibrinogenemia were independent predictors of major complications. Further studies are pending in order to draw definitive conclusions.