Abstract Background Severe anaemia after caesarean section adversely affects the woman and the new-born. While prenatal anaemia is extensively studied, the literature on post-caesarean section anaemia is limited and characteristics of women at the highest risk of developing severe anaemia after caesarean section are unknown. This study aimed to determine the prevalence and factors associated with severe anaemia on day three post caesarean section. Methods On the third day after caesarean section, women were consecutively enrolled in a cross-sectional study at Mbarara Regional Referral Hospital (MRRH). Women who got transfused peripartum were excluded. For every woman, we measured haemoglobin (Hb) concentration and collected data on sociodemographic, obstetric, and medical characteristics. The primary outcome was severe anaemia after caesarean section, defined as Hb