Background: Failure to visit antenatal care earlier can result in potential complications during pregnancy, delivery and puerperium. Despite ANC is provided free of charge and there is increased accessibility; low utilization and late initiation is still a major problem. The studies in the past show the magnitude and prevalence of late initiation of antenatal care visit but there is limited information on determinants of late initiation of antenatal care visit. Objective: To assess the determinants of late initiation for first ANC visit among pregnant women in public health facilities at Kembata Tembaro zone, South Ethiopia, 2021. Methods- Institution basedunmatched case-control study design was conducted among 306 (102 cases and 204 controls) pregnant women in Kembata Tembaro zone from June to July2022. Multi-stage sampling technique was employed. The questionnaire was developed using Kobo Toolbox and data was collected with face to face interview of mothers or immediate caretakers of the child using mobile device.The data was analyzed using SPSSversion 25. Bivariable and multivariable logistic regression analysis was used to identify the determinants of late initiation for the first ANC visit.Adjusted odds ratio (AOR) with 95% CI and p-value<0.05 was used to declare statistical significance. Result – Multivariable logistic regression analysis identified four determinants of late initiation for first ANC visit. A mother being illiterate [AOR=7.19, 95%CI (1.98-26.13)], lack of previous ANC follow up [AOR=4.22, 95%CI (1.53-11.63)], unplanned pregnancy [AOR=5.01, 95%CI (2.12-11.83)], and poor knowledge of the mothers about ANC[AOR=3.11, 95% CI (1.42-6.79)] were identified as the determinants of late initiation for first ANC visit among pregnant women. Conclusion-This study revealed that a mother being illiterate, lack of previous ANC follow up, having unplanned pregnancy, and poor knowledge of the mother about ANC were determinants of late initiation for first ANC visit among pregnant women. Focus should be given to improve women’s knowledge on early ANC service utilization and empowering women is essential.