CONTEXT AND OBJECTIVE: Ethiopia's primary care has a weak referral system for sick children. We aimed to identify health post and child factors associated with referrals of sick children 0-59 months of age and evaluate the healthcare providers' adherence to referral guidelines. DESIGN: A cross-sectional facility-based survey. SETTING: This study included data from 165 health posts in 52 districts in four Ethiopian regions collected from December 2018 to February 2019. The data included interviews with health extension workers, assessment of health post preparedness, recording of global positioning system (GPS)-coordinates of the health post and the referral health centre, and reviewing registers of sick children treated during the last 3 months at the health posts. We analysed the association between the sick child's characteristics, health post preparedness and distance to the health centre with referral of sick children by multivariable logistic regressions. OUTCOME MEASURE: Referral to the nearest health centre of sick young infants aged 0-59 days and sick children 2-59 months. RESULTS: The health extension workers referred 39/229 (17%) of the sick young infants and 78/1123 (7%) of the older children to the next level of care. Only 18 (37%) sick young infants and 22 (50%) 2-59 months children that deserved urgent referral according to guidelines were referred. The leading causes of referral were possible serious bacterial infection and pneumonia. Those being classified as a severe disease were referred more frequently. The availability of basic amenities (adjusted OR, AOR=0.38, 95% CI 0.15 to 0.96), amoxicillin (AOR=0.41, 95% CI 0.19 to 0.88) and rapid diagnostic test (AOR=0.18, 95% CI 0.07 to 0.46) were associated with less referral in the older age group. CONCLUSION: Few children with severe illness were referred from health posts to health centres. Improving the health posts' medicine and diagnostic supplies may enhance adherence to referral guidelines and ultimately reduce child mortality.