Background: Access to antiretroviral drugs for all infected persons in need is a global health priority. The viral load and CD4 counts should be monitored regularly. The plasma viral load should be reduced by as much and for as short as possible. Identifying factors that predict time to viral load suppression of patients on antiretroviral therapy regimens is thus vital to optimizing therapeutic success. Therefore, this study aimed to estimate the time to viral load suppression and identify predictors of time to viral load suppression of patients on antiretroviral therapy at Arba Minch general Hospital.Methods: This study was observational study using data abstracted from medical records, patient interviews and laboratory work-up during 6 months of follow up. The data were collected from 152 naive to anti-retro viral drug patients. The univariable and multivariable Cox proportional hazard regression analyses were done to identify predictors.Result: The median survival time of viral load suppression among adult patients living with HIV was 3 months with 95% CI (2.68, 3.32). The Cox-proportional hazard analysis shows baseline CD4 count of <200cells/mm3 (AHR=0.683, CI:0.471, 0.990), baseline viral load of <10,000 copies/ml (AHR=4.135, CI:1.835, 9.317), having baseline Cotrimoxazole preventive therapy (AHR=1.997, CI:1.108, 3.600), having baseline Isoniazid preventive therapy (AHR=3.085, CI:1.721, 5.529) and good adherence level to ART (AHR=2.648 ,CI: 1.202, 5.834) significantly predict the time to viral load suppression.Conclusion: Early improvement and maintenance of CD4 count and viral load to normal level should be attained through streamlining and strengthening monitoring and counseling of patients on adherence to ART, Cotrimoxazole and Isoniazid drugs.