Background: Viral suppression is critical for pregnant and breast-feeding women, but limited data are available on Human Immune Virus (HIV) of pregnant and breast-feeding mother and who are on antiretroviral therapy (ART) and factor associated with viral load suppression in Bahidar city are not well addressed. Objective: To asses magnitude of viral load suppression and associated factors among HIV positive pregnant and breast-feeding women receiving ART in Bahir Dar city administration Health facilities North West Ethiopia 2020. Method: Institutional based cross-sectional study was conducted among 423 HIV positives pregnant and breast feeding mothers who started ART in Bahir dar city administration from March 2019 to May/2020. Systematic sampling technique was used to select the study participants. A structured questionnaire was used for data collection information .The Data was entered using Epi Data software version 3.1 and analyzed using SPSS version 23 software. Bi variable and multivariable Logistic regression analysis was used. In the bi-variable analysis, p- value of less than 0.25 was used to select candidate variables for the multivariable logistic regression and data were interpreted using adjusted odds ratios and 95% confidence intervals (CI) for all outcome variables. P-values less than 0.05 were the cut point to say the variables statistically significant. Result: A total of 423 patients participated on the study yielded a response rate of 100%.The magnitude of viral load suppression in this study was 95.3%. Mothers who married (AOR=6.272; 95%CI: 1.971, 19.958), ART taken for 12-24 months (AOR=5.964; 95%CI: 1.672, 21.279), good adherence of ART medication (AOR=6.735; 95%CI: 1.859, 24.400), were significantly associated with viral load suppression. Conclusion: The magnitude of viral load suppression was good. Married women, participants who took ART for 12-24 months and from 25-35 months, good adherence of ART medication and no drug side effects were factors associated with viral load suppression. Hence, the government and other concerned stakeholders should give due attention on the adherence counseling and support, Mothers who had HIV positive and single should get special attention and counseling to improve their viral load suppression and stronger counseling regarding ART drug side effect to sustained viral load suppression. Keyword: HIV/AIDS, Viral load suppression, pregnant, breast-feeding