Background: Diversified diet to improve better tolerates human immunodeficiency virus drugs, enhance antiretroviral therapy adherence and maintain a healthy weight to reduce mortality and morbidity. Therefore, the aim of this study was to assess dietary diversity and associated factors among adult human immunodeficiency virus positive patients who were on antiretroviral therapy at Debre Tabor Hospital northwest EthiopiaMethods: Institutional based cross-sectional study was conducted at Debre Tabor Hospital and participants selected by the systematic random sampling techniques. Data collection was done by using a structured interview questionnaire. Dietary diversity was computed from all food and drink list consumed in the 24 hours preceding the survey. A variable having p- value < 0.2 in the bivariate logistic regression was entered into the multivariable logistic regression, and independent variables having p-value < 0.05 was considered as significantly associated. Results: Of the total 341 adults on antiretroviral therapy 336 participants gave a complete response with a response rate of 98.50%. Among the participants 336 [32.4% (95% CI: 27.4, 37.1)] had adequate dietary diversity and 22.9% were BMI <18.5kg/m2. Government employment [AOR= 2.5; 95%CI: 1.28, 4.98) and diploma and above educational status [AOR=2.3; 95% CI: 1.01, 5.31) were factors for adequate dietary diversity. Conclusions: In this study the magnitude of adequate dietary diversity was low. Employment and educational status were significantly associated with dietary diversity among people living with HIV/AIDS. Hence, improving education status as well as income generation activities are highly recommended strategy to improve the dietary diversity of patients on antiretroviral therapy.