Introduction Hepatitis B virus disease is a global acute and chronic communicable disease. Mother-to-child transmission is the reason for high carrier rates. Unvaccinated newborns infected through mother-to-child transmission are at >95% risk of developing chronic hepatitis B virus disease. Vaccination is the most effective measure to reduce the global incidence of hepatitis B virus disease. Despite the World Health Organization's target to achieve 90% of the hepatitis B vaccine birth dose by 2030, little is known about the vaccination status of exposed newborns. Objective The present study aimed to determine the timing of the hepatitis B vaccine birth dose in exposed newborns in Southwest Ethiopia. Methods An institution-based cross-sectional study was employed on 422 systematically selected exposed newborns from April 2, 2022, to August 28, 2022. A pretested, interviewer-administered questionnaire was used for data collection. Data were entered into Epi data 3.1 and exported into SPSS version 23 software for analysis. Both bivariable and multivariable binary logistic regressions were performed. Variables with a p -value