Aim: Low motivation is a core symptom of schizophrenia which significantly impacts successful engagement in and benefit from psychosocial treatments. Therefore, it is important for clinicians to design psychosocial treatments to effectively motivate and engage patients during the treatment. The MUSIC® Model of Academic Motivation Inventory (MMI) is an 18-item instrument with five scales that assess students' motivation during academic tasks. The objective of the current study was to validate the MMI for use with schizophrenia-spectrum patients undergoing cognitive training. Methods: Participants included 181 people with schizophrenia spectrum disorders enrolled in cognitive training in four countries. A confirmatory factor analysis (CFA) assessed construct validity. Quality of fit was determined using the Comparative Fit Index (CFI), the Standardized Root Mean Square Residual (SRMR), and the Root Mean Square Error of Approximation (RMSEA). Pearson's correlation coefficients assessed construct validity and Cronbach's alphas assessed reliability. Furthermore, we examined factor loadings for each inventory item and assessed predictive validity by analyzing MMI scales with attendance outcomes. Results: Consistent with the original MMI validation studies used in academic settings, we found CFI values indicated a good fit, as did the SRMR and RMSEA values. The scales were correlated yet distinct. Cronbach's alpha values ranged from good to excellent and factor loadings showed that all items loaded very well onto their intended factors. The MMI had a positive relationship to treatment intensity. Conclusion: The MMI is a valid and reliable tool to use with individuals with schizophrenia spectrum disorders undergoing a cognitive training intervention.