Background Maternal and neonatal health continuum of care (MNH CoC) is one of the recommended strategies for reducing maternal and neonatal deaths. However, its utilisation remains low in sub-Saharan Africa, including Ethiopia. The purpose of the study was to determine the magnitude of maternal and neonatal continuity of care utilisation and identify determining factors in Assosa Zone, North Western Ethiopia.Method Facility based cross-sectional study design was used to conduct the study from January to March. Proportional allocation of samples to health facilities and simple random sampling followed by systematic sampling was used to select a sample of 564 women who had given birth in the preceding nine months before data collection for the study. Data was collected through the use of a questionnaire. The data was analysed using SPSS version 27 software.Result The overall completion of maternal and neonatal CoC services in the antenatal, childbirth and postnatal periods was 53.7%. The study showed that factors such as education, occupation, partner support, knowledge of the expected number of antenatal visits, early booking of antenatal care, places of ANC, place of PNC, comprehensive counselling and physical examination during ANC, and mode of delivery were significantly associated with completion of MNC CoC services. However, the odd of completion of MNH CoC services were decreased by 21% (AOR = 0.21, 95%CI = 0.09–0.51) among women who had knowledge of neonatal danger signs or complications than their counterparts.Conclusions The completion of MNH CoC services was low among women and many women did not receive lifesaving intervention along the continuum of care pathways. Hence, compressive awareness raising, education, counselling and empowering of women in health care at the household, community and facility level required to improve the completion of maternity continuum of care.