Background: Late antenatal care initiation is the initiation of antenatal care by pregnant women after the recommended time (≤ 12 weeks of gestation) passed. It relates with maximizing maternal and fetal morbidity and mortality. Even if early antenatal care seeking is essential and many strategies applied, gaps related with late antenatal care initiation was not minimized. Objective: The study aimed to determine proportion and associated factors with late antenatal care initiation among pregnant women in Mehal Sayint district, South Wollo Zone, Ethiopia, 2019. Methods: Facility based cross-sectional study conducted in Mehal Sayint district from August 10 - September 20/ 2019. Pregnant women who come to attend antenatal care at selected health facilities were a study population. Total sample size was 421 by using single population proportion. Study participants was selected using systematic random sampling technique. Data was entered by Epi info 7 and statistical package for social sciences version 25 was used for analysis. Variables with P-value < 0.2 at 95% confidence interval in Bivariable logistic regression was included in multivariable logistic regression. Variable with P-value of < 0.05 at 95% of confidence interval in multivariable logistic regression was declared as significant. Hosmer–Lemeshow model was used to check goodness of fit. Result: The proportion of late antenatal care initiation (>12 weeks) was 74.60% with 95% CI (70% to 79%). On multivariable regression analysis the odds of late ANC initiation for pregnant women from rural place of residence was 6.73 times the odds of late ANC initiation for women from urban place of residence (AOR= 6.73 CI: 3.79, 11.93), the odds of late ANC initiation for pregnant women not attending ANC conference was 2.59 times the odds of late ANC initiation for women attending ANC conference (AOR=2.59, CI: 1.48, 4.54), the odds of late ANC initiation for women not use FP before current pregnancy was 4.27 times the odds of late ANC initiation for women utilize family planning before current pregnancy (AOR=4.27, CI: 2.10, 8.69), the odds of late ANC initiation for pregnant women with no knowledge about ANC was 2.77 times the odds of late ANC initiation for women have knowledge about ANC initiation (AOR= 2.77, CI: 1.28, 5.98) and the odds of late ANC initiation for pregnant women not disclose pregnancy status was 2.42 times the odds of late ANC initiation for women who disclose pregnancy status (AOR=2.42, CI: 1.33, 4.43) were found factors associated with late antenatal care initiation. Conclusion: Proportion of late antenatal care initiation was high. Rural residence, not attending antenatal care conference, poor knowledge about antenatal care, not use family planning before pregnancy and not disclose pregnancy status were factors associated with late initiation. Awareness creation on benefits of family planning and attending antenatal care conference and provide health information for rural population about antenatal care should be undertaken. Key words: Late antenatal care initiation, pregnant women, cross-sectional, Mehal Sayint district