Background: In the past two decades the implementation of highly active anti-retroviral therapy recovers the immune status and reduces unwanted outcomes on people living with Human Immunodeficiency Virus (HIV). However, the emergence of treatment failure and drug resistance leads to an increased morbidity, mortality and compromised quality of life on people living with HIV. Objective: The aim of this study was to determine first line antiretroviral treatment failure and identify associated factors among people living with human immunodeficiency virus in Bahir Dar, North West Ethiopia Methods: A facility based cross sectional study was conducted from November, 2017 to April, 2018. Patients’ socio-demographics and clinical data were collected using structured questioner. Blood sample was taken and tested for viral load, complete blood cell count (CBC), Chemistry (ALT & Creatinine) and CD4 count following the standard protocols. Two consecutive viral load analyses were done: during the time of enrollment and after three months of intensive follow-up for those with first viral load >1000 RNA copies/ml. Treatment failure was reported when there was viral load of >1000 RNA copies/ml. Data were entered and analyzed with SPSS version 23. Descriptive statistics such as frequency, percentage, mean and logistic regressions were utilized. A p value of <0.05 was considered as significant. Results: A total of 430 HIV positive people who had ≥6 months of antiretroviral (ARV) treatment follow up were included. Of these 57.9% were females. The mean age was 38 years (ranges 12-67 years).The mean months of ART follow up was 83 months. In the first viral load run, 106 (24.7%) of the cohort were treatment failed. After 3 months of intensive adherence support, the prevalence down to 65(15.1%) resulting 41(38.7%) re-suppression rate. Male gender, drug discontinuation history, poor adherence, irregular time of drug intake, base line and current CD4 counts <200 cells/ml and having multiple sexual behavior showed significant association with treatment failure. Conclusions: In this study, first line HIV treatment failure was 15.1% and re-suppression rate of second viral load was 38.7% among first viral load failed patients. Gender of male, drug discontinuation habit, had multi sexual partner, sub-optimal adherence and lower baseline and current CD4 counts were the factors contributed for treatment failure. Keywords: HIV, treatment failure, ART