Background: Early initiation of antenatal care is the first antenatal care visit received before 16 weeks of gestation. Early initiation of antenatal care is a tremendous effect on both maternal and fetal health by early detection, managing and preventing adverse outcomes of pregnancy. However, in the world including Ethiopia, significant numbers of pregnant mothers were not initiate early antenatal care on the recommended time. Objective: To assess the proportion and factors associated with early initiation of antenatal care among pregnant women attending antenatal care service at Bahir Dar city public health centers, Bahir Dar, Ethiopia. Method: An institutional based cross sectional study was conducted. A total of 592 pregnant women have participated. Participants was selected using Systematic sampling technique. Data were collected through the interviewer structured and pre tested questioner. Data were entered by using Epi data version 4.6 software and exported to SPSS version 23 for analysis. Bi variable and multi variable logistic regression models were used to identify the associated factors with the outcome variable. On bi variate analysis p-value, less than 0.2 was used to select the candidate variable for multi variable analysis. P-value were used to measure the level of significance on multivariable analysis and those variables whose P-value <0.05 were considered as statically significant. The strength of association was assessed using odds ratio with 95% CI. Result: Two hundred eighty-eight (48.6%) started first antenatal care before 16 weeks of gestation. The result showed that family size less than five (AOR= 2.0, 95%CI;1.25-3.25), urbans (AOR=3.0,95%CI;1.48,6.17), secondary education (AOR=2.1,95%CI;1.3-3.6), college level and above (AOR=3.5,95%CI;1.8-6.8), primi gravida (AOR=2.6,95%CI;1.65-4.14), planned pregnancy (AOR=3.5,95%CI;1.5-8.1) and knowledgeable on early initiation of antenatal care (AOR= 1.7, 95%CI; 1.14-2.55), were significantly associated with early initiation of first antenatal care. Conclusion: The study showed that almost half of the participants had early initiation of antenatal care and high compared to EDHS. This study indicated that family size, residence, educational status of women, gravidity, plan of pregnancy and knowledge on early initiation of first ANC were factors significantly associated with early initiation of antenatal care service. Keywords: Antenatal care, early initiation, pregnancy