Background: Obesity is on the rise worldwide, not only in the general population but also in PLWHA. Being overweight and obese are themselves a risk factors for cardiovascular and other diseases. Despite this few studies have been conducted to determine the magnitude of obesity/overweight and its associated factors among HIV/AIDS patients in Ethiopia. This study aimed at determining the magnitude of obesity/overweight and its associated factors among HIV/AIDS patients on HAART at JUSTH, Ethiopia 2019. Method: hospital based cross-sectional study was conducted from January to February in 2019 at JUSTH. WHO STEP wise approach to chronic disease risk factor surveillance (STEPS) questionnaire and document review for HIV related clinical factors was applied. Weight, height and waist circumference and hip circumference were measured. BMI ≥25 kg/m2 was considered overweight, while abdominal obesity was referred to males with waist to hip ratio of greater than 0.95 and greater than 0.85 for females. Data was analyzed using SPSS version 20. Results: A total of 252 participants with a response rate of 95.8% were included. The prevalence of obesity/overweight was 21%. After adjusting for these variables, age category of greater than 50 years [AOR = 0.4, 95%CI (0.2, 0.9), p = 0.03],WHO clinical stage III and above [AOR = 0.04,95% CI (0.002,0.6) ), p = 0.02], presence of mild to moderate physical activity [AOR = 1.3,95% CI,(5.5,33.3)),p=0.00), plasma CD4 count between 351-500 copies/ml [AOR=0.15,95% CI, (0.04,0.6) p=0.024], female sex [AOR = 2.6,95% CI,(1.25,10)p=0.03)] were significantly associated with obesity/overweight Conclusion: There was a high prevalence of obesity/overweight among HIV/AIDS patients. It was found that older age , female sex , early stage of the disease, lower CD4 cunt and absence of mild to moderate physical activity were significant predictor of obesity/overweight. Clinicians should be aware of the health consequence of obesity and consider instituting targeted weight management programs as part of routine HIV care. It is, therefore, vital to encourage intervention strategies that focus on promotion of physical activity among people living with HIV/AIDS.