Antenatal care is more beneficial in preventing adverse pregnancy outcomes when received early and continued till delivery. World Health Organization (WHO) recommends at least four antenatal care visits for women with no complication. Conversely, survey data from Ethiopia showed that only one third are initiated early. Thus, assessing magnitude and factors affecting antenatal care (ANC) completion is required for public health intervention planning and implementations. Accordingly, this study is conducted with the aim of assessing factors affecting ANC completion among mothers attending delivery and postnatal service in Jimma town health facilities. Institution based cross-sectional study design was employed from March to April 2016 in Jimma town. Three hundred and sixty six mothers who came for delivery and postnatal service were selected using simple random sampling technique. Interviewer administered questionnaires were used to collect data. The data were entered into EPI data version 3.1 and analyzed using SPSS for Windows, version 20. Regression analyses were used to isolate independent predictor's antenatal completion. A total of 366 participants of the study, 364 underwent all the study components giving a response rate of 99.4%.