Objective: To investigate the effect of obturator nerve blockade on oncological outcomes of patients with a diagnosis of lateral wall localized non-muscle invasive bladder cancer. Materials and Methods: One hundred six patients diagnosed with lateral wall localized non-invasive bladder cancer were evaluated between January 2015 and March 2020 in this retrospective, cross-sectional observational study. The patients were divided into two groups: patients receiving only spinal anaesthesia and those receiving spinal anaesthesia combined with ultrasound-guided obturator nerve blockade. Oncological outcomes of the groups were compared statistically. Results: We observed recurrent tumours in 25 patients (45.5%) in Group 1 and 11 patients (21.6%) in Group 2. In addition, we observed tumour progression in eight patients (14.5%) in Group 1 and two patients (3.9%) in Group 2. We observed statistical significance in differences between groups regarding tumour size, recurrence rate, adequate muscle tissue sampling, the ability for complete resection and persistent obturator reflex. The efficacy rate of obturator blockade was 92.1% in Group 2. One-year recurrence-free survival (RFS) was 98.0% and five-year RFS was 23.5% for Group 1, while they were, respectively, 97.4% and 57.2% for Group 2. Conclusion: The obturator reflex is a common and challenging reflex that may cause major complications and result in unintended consequences such as incomplete resection or tumour recurrence with transurethral resection of bladder tumours. In this study, we demonstrated that combining spinal anaesthesia with obturator nerve blockade for lateral wall localized non-muscle invasive bladder cancer may prevent tumour recurrence and reduce perioperative complications.