Background: Patients with muscle invasive bladder cancer who undergo platinum-based neoadjuvant chemotherapy (NAC) followed by radical cystectomy or radiotherapy are at high risk of venous and arterial thromboembolic events (TEE). TEE is associated with delay to radical cancer treatment, significant morbidity and even mortality. This study aimed to document the incidence and characteristics of TEE during NAC and prior to radical treatment. Methods: Retrospective data was collected on all patients in our centre who underwent NAC prior to radical treatment. TEE events were identified based on routine imaging to assess for response to NAC; or imaging based on clinical symptoms developed during (or within 28 days) of NAC but prior to radical treatment. Results: Data was collected on 148 patients between January 2015 and September 2023. Age range: 44 - 82 years, the majority (73.6%) of whom were male. All patients received platinum-based chemotherapy (median 4 cycles). A total of 31 patients (20.9%) developed 35 TEE, including 27 venous events (24 pulmonary emboli and 3 deep venous thromboses), and 8 arterial events (3 aortic thrombus, 4 limb ischaemia, 1 ischemic stroke). Four patients had a venous and arterial TEE. The majority of pulmonary venous TEE were subclinical. Conclusions: Our single-centre study demonstrates that the incidence of TEE during NAC prior to radical treatment for bladder cancer is high. Improved imaging techniques and routine scans post-NAC led to identification of subclinical TEE that require treatment as they are likely to become clinically significant. The high rate of TEE in this patient population is likely to benefit from prophylactic anticoagulation during NAC and should be investigated in future prospective clinical trials.