Introduction: Occupational performance as an integrating concept allows a holistic assessment of the person and identifies their potential for the return of productive activities through the occupational concept as an input for the assessment of the Loss of Work Capacity, allowing an objective score of the aspects that constitute the Single Manual for Evaluation of the Loss of Labor and Occupational Capacity. Methods: Analytical cross-sectional study with application of an occupational performance evaluation scale to a sample of conveniently selected workers with alterations in functions or body structures, participation or restriction at the occupational level. Analytical comparisons were made with the Manual for Evaluation of the Loss of Labor and Occupational Capacity scoring standard, and differential and integrating factors were identified. Results: 6 subjects made up the sample, 4 had an occupational accident and 2 had an occupational disease. Regarding the performance evaluation, it was evidenced that 66% presented mild dependence on specific activities and that as a result it was possible to perform a differential analysis with the Manual for Evaluation of the Loss of Labor and Occupational Capacity score. Specific factors are recognized in the assessment process such as the objectivity of the occupational performance assessment, the multiple contributions of the concept of occupational performance in the understanding of the assessment to the Loss of Work and Occupational Capacity, and the possibilities of articulation with the Manual for Evaluation of the Loss of Labor and Occupational Capacity. Conclusions: The assessment of occupational performance and the comprehensive concept of the occupational therapist are constituted as a fundamental axis that contributes to the process of assessment of the loss of work and occupational capacity.