Objectives: To measure the coverage of antenatal syphilis screening and identify factors related to women not being screened. Goal: To assess the syphilis control program in Mongolia. Study design: Antenatal care records of women in 16 antenatal care clinics of 6 districts were reviewed. Additionally, postpartum women were interviewed to identify potential factors for not being screened. Results: Among 3519 antenatal records, the coverage of syphilis screening was 77.7%. Of 2735 screened women, 54 (2.0%) had reactive serological results and subsequently received treatment. Four late antenatal care comers delivered infants with congenital syphilis. Being unscreened was significantly associated with late antenatal care (odds ratio OR = 2.6), lack of knowledge (OR = 5.5), history of previous sexually transmitted infection (OR = 3.7), and living far from screening services (OR = 4.9). Conclusions: The coverage of antenatal syphilis screening is still low, with poor contact tracing. More efforts are needed to promote early antenatal care visit and improve syphilis screening systems.