Aims: To establish the prevalence, determinants and the antibiotic susceptibility pattern of Group B streptococcus in pregnant women in Sagamu, Ogun State, Nigeria. Study Design: Prospective cross-sectional study Place and Duration of Study: The study was carried out at the antenatal clinic at Olabisi Onabanjo University Teaching Hospital, Sagamu, Ogun State, Nigeria, between July 2017 and December 2017. Methodology: The study involved 184 pregnant women attending antenatal clinic. Lower vaginal and rectal swabs were collected under aseptic condition and immediately sent to the laboratory for processing. The samples were assayed for the presence of group B streptococcus using conventional methods. Information on the socio demographic characteristics and details of delivery were recorded on a data capture sheet. Results: The prevalence of Group B streptococcus was 27.7%. The odds of Group B streptococcus colonization was significantly higher among women of low parity (? 2) and binary logistic regression analysis showed that parity was predictive of Group B streptococcus colonization (OR 3.7; 95% CI = 1.03-13.46; P=.045). Younger women (age ? 30 years) and women carrying term pregnancies had a non significant trend towards higher odds of Group B streptococcus colonization [(OR= 1.22, 95% CI: 0.6-2.3, P = .54) and (OR=1.6, CI: 0.8-3.2; P = .15) respectively]. The resistance of group B streptococcus isolates to penicillin and ampicillin was 39.2% and 37.3% respectively. Conclusion: The group B streptococcus colonization rate in this study is high. Factors such as low parity, young maternal age and term pregnancies are associated with increased odds of colonization. The emergence of resistance to the commonly prescribed antibiotics calls for reevaluation of the current recommendations regarding the antibiotics prophylaxis.