INTRODUCTION: Antenatal care (ANC) is important for both maternal and fetal health. However, the existing evidence from developing countries indicates that most pregnant women attending ANC in their late pregnancy. Little is known about the factors determining ANC booking and the content of care among pregnant women in West part of Ethiopia. Therefore, the present study was conducted to identify factors determining late ANC booking and the content of care among pregnant mother attending antenatal care services in East Wollega administrative zone, West Ethiopia. METHODS: Institutional based cross-sectional study was conducted from July to September, 2014 among 421 pregnant women's attending ANC services in purposively selected health facilities, East Wollega zone, Ethiopia. The pretested-structured questionnaires were used to collect socio-demographic data and predictor factors of late initiation of ANC services. Five trained nurse working at ANC clinic at each health institution administered the questionnaire. The collected data was analysed using SPSS version 20. RESULTS: The prevalence of late ANC booking was 81.5% (343/421) in the study area. Being from Oromo ethnic group (AOR 4.27, (95% CI, 1.48-12.33)), maternal age equal or more than 25 year old (AOR 3.09 (95% CI, 1.53-6.27)), second trimester (AOR 6.05(95% CI, 3.08-11.88)) and third trimester (AOR 7.97 (95% CI, 3.92-16.23)) were main factors identified as contributing (favoring factors) for the likely occurrence of late booking for ANC whereas; monthly income more than and/or equal to 15000 Ethiopian birrs (AOR 0.38 (95% CI, 0.18-084)) were factors compromising (decreasing) the chances for late attendance for the services among the pregnant women. CONCLUSION: Late ANC initiation is high in the study area despite the services is provided free of charge. Hence, it is important to provide health education on the timing of ANC among women with reproductive age. Community's awareness on importance of receiving early ANC also needs to be promoted.