Background National Institute of alcohol and alcoholism define Problem/risky use of alcohol as drinking in a way that can negatively impact our health and life, but the body is not physically dependent on the substance. Risky alcohol use behavior is harmful to both the fetus and the mother such as maternal alcohol intoxication and alcohol use disorder, abortion, stillbirth, low birth weight, and prematurity. This study is aimed to assess the prevalence of risky alcohol use for both the mother and the fetus during pregnancy among mothers who have used alcohol at least once in the current pregnancy. Methods Institution based cross-sectional study was conducted among a total of 380 mothers who have used alcohol at least once during the current pregnancy. The participants were selected using a systematic random sampling technique. Both Bivariable and Multivariable Binary Logistic Regression models were done to identify associated factors. Odds Ratios with their 95% Confidence Interval was computed and variables with a p -value < 0.05 during multivariable analysis were considered significantly associated factors. Results A total of 380 mothers who used alcohol at least once (any amount) in the current pregnancy were included in the study and further interviewed for risky alcohol use behavior with a response rate of 100%. The overall prevalence of risky alcohol use behavior was 16.1% (95% CI = 12.1, 19.7). Having poor social support, having moderate to severe depression and anxiety, having diagnosed family history of mental illness, having a history of abortion were important factors which significantly associated with risky alcohol use behavior. Conclusion Significant proportions of pregnant mothers were risky alcohol drinkers. It will be better if screening of any amount of alcohol use during pregnancy and providing health education (about the risk of alcohol use) for all pregnant women who attend antenatal care follow up.