Objective: The primary aim was to determine the performance of neoadjuvant chemotherapy VI-RADS (nacVI-RADS) in predicting response to systemic therapy in patients with MIBC and to evaluate its inter-reader agreement., Materials and Methods: Prospective study, including patients with non-metastatic muscle-invasive bladder cancer (MIBC) who underwent neoadjuvant chemotherapy before radical cystectomy (RC). Patients underwent pre- and post-treatment MRI. Radiological response was evaluated by two experienced radiologists using nacVI-RADS scoring system. Reference standard was defined using histopathological findings. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy were calculated to assess nacVI-RADS performance for each reader. Inter-reader agreement was determined with Cohen's k statistics., Results: Fifty-five patients with non-metastatic MIBC, 46 males (84%) and 9 females (16%) with a median age of 69 (interquartile range (IQR) 66-72 years) were enrolled. Diagnostic performance of nacVI-RADS in detecting complete response to neoadjuvant chemotherapy showed a sensitivity of 76.5-85.3% and specificity of 76.2-81%. The area under the curve was 0.93 (95% CI: 0.86-0.99) for detecting any residual tissue, for the more experienced reader. Inter-reader agreement was optimal with a K of 0.85. In the multivariable logistic regression model, the variables showing independent correlation with response prediction to neoadjuvant therapy were nacVI-RADS score (p = 0.01 for the more experienced reader) and tumor regression grade (TRG; p < 0.001)., Conclusion: NacVI-RADS scoring system offers a reliable and reproducible approach, employing a well-structured and easily interpretable method, to assess the response to systemic therapy in patients with MIBC., Key Points: Question There is a lack of a standardized approach to distinguish between responders and non-responders to neoadjuvant chemotherapy for muscle-invasive bladder cancer. Findings The neoadjuvant chemotherapy VI-RADS (nacVI-RADS) score diagnostic performance for detecting complete response to neoadjuvant chemotherapy showed 85.3% sensitivity, 81% specificity, and an AUC of 0.93. Clinical relevance NacVI-RADS score represents a valid predictor of response to neoadjuvant systemic therapy, impacting therapeutic decision-making and improving overall patients' management., Competing Interests: Compliance with ethical standards. Guarantor: The scientific guarantor of this publication is Valeria Panebianco. Conflict of interest: R.G. is a Deputy Editor for European Radiology. V.P. is a member of the Scientific Editorial Board for European Radiology (section: urogenital). They did not participate in the selection or review processes for this article. The other authors declare no conflicts of interest. Statistics and biometry: No complex statistical methods were necessary for this paper. Informed consent: Written informed consent was obtained from all subjects (patients) in this study. Ethical approval: Institutional Review Board approval was obtained. Study subjects or cohorts overlap: Not applicable. Methodology: Prospective Observational Multicenter enrollment , (© 2024. The Author(s), under exclusive licence to European Society of Radiology.)