Background: HIV-induced malnutrition is highly prevalent in different parts of the world particularly in sub-Saharan Africa. The food intervention package is one of the strategies that targets malnutrition among HIV-infected people through nutritional evaluation, counseling and care. However, little is known concerning the outcomes of intervention in such patients in treatment program. Therefore, this study aimed to assess nutritional treatment outcomes and its predictors among adult HIV-positive undernourished individuals in Ethiopia. Methods: Facility based retrospective cohort study was deployed in Adult Antiretroviral therapy clinic of Hawassa University Comprehensive Specialized Hospital. Data of 419 patients were extracted from the food by prescription registration book and patient cards using structured questionnaires. Statistical significance was assessed using Cox-proportional Hazard model by determining hazard ratios and 95% confidence interval. Results: The proportion of adult HIV patients who recovered from malnutrition after they were enrolled in the food by prescription therapy was 53.0%. The variables found to have an association with good nutritional treatment outcomes of food by prescription in the final model are being female (