Background: Pertussis is a life-threatening type of infection in non-immune infants younger than six months of age. Vaccination of pregnant women with tetanus, diphtheria, and pertussis vaccine (Tdap) may facilitate the transfer of maternal antibodies to the fetus, this method may provide protection against pertussis in these newborns. This study will examine the seroprevelance of Bortedella pertussis antibodies in pregnant Saudi females. Methods: This is a crosssectional study in which 258 pregnant females of different age groups in the second and third trimesters who underwent antenatal checkups at King Saud University Medical city, Riyadh, between April 2017 and March 2018 were enrolled. Serum levels of B. pertussis antibody were measured using the enzyme-linked immunosorbent assay (ELISA) technique. Results: From 258 blood samples,234(90.69%) females between 28 and 45 years of age were non immune to pertussis,12(4.6%) showed borderline immunity, and 12(4,6%) were immune. Conclusion: The majority of tested pregnant Saudi females were non-immune to B.Pertussis despite the expanded Saudi program of immunization (which recommends that the last dose of DTap be given to preschool-age children). This study emphasizes the importance of implementation of Tdap vaccination program in pregnant Saudi females.