Background: During pregnancy, due to the physiological and hormonal change, the requirement of iron–folic acid is enhanced. Therefore, the occurrence of iron/folic acid deficiency is relatively high and it is responsible for 95% of anemia during pregnancy. Objectives: The aim of this study was to assess adherence to prenatal iron–folic acid supplementation (IFAS) and associated factors among pregnant women attending antenatal care services at public health facilities of Dilla town. Methods: Facility-based cross-sectional study design was employed selecting 403 pregnant women attending antenatal care services in three public health institutions of Dilla town. The women were included in the study by simple random sampling. Data were collected by interview and document review. Then it was entered into EPI Data version 3.1 and exported to SPSS version 20 for analysis. Bivariate and multivariate binary logistic regression techniques were used to identify independent predictors. A p-value <0.05 was taken as indication of statistical significance. Results: From the total of planned 403 pregnant women, 396 participated in the study, with a response rate of 98.2%. Of these, 172 (43.4%) pregnant women were adhered to IFAS. The study also revealed that history of previous anemia (adjusted odds ratio (AOR) = 1.87; 95% confidence interval (CI): (1.01–3.47); p = 0.04), frequency of antenatal care center (ANC) visits (AOR = 2.51; 95% CI: (1.17–5.37); p = 0.01), knowledge of IFA supplement (AOR = 2.28; 95% CI: (1.36–3.82); p = 0.002), and knowledge of anemia (AOR = 2.30; 95% CI: (1.40–3.77); p = 0.001) were independent predictors of adherence to IFAS. Conclusion: The finding of this study showed that less than half of the pregnant women were adhered to IFAS. History of previous anemia, frequency of ANC visits, knowledge of IFA supplement, and knowledge of anemia were the factors associated with adherence to IFA supplement.