Across several African countries, birth preparedness and complication readiness (BPACR) among pregnant women is poor. The practice of BPACR, though improving in recent years, is not commensurate with the knowledge available to pregnant women. Maternal health indices remain sub-optimal. This study evaluates the determinants of this "know-do' gap among women receiving antenatal care at a secondary health facility in Benin City, Nigeria. A cross-sectional study involving 427 pregnant women was conducted between October and December 2020 using a structured interviewer-administered questionnaire. The prevalence of knowledge and practice were described, and the determinants of BPACR practice evaluated using bivariable (chi-square) analysis and multivariable ordinal logistic regression with post-estimation predictive margins analysis. About 77% of respondents had good birth preparedness practice. Multivariable regression revealed that respondents with poor knowledge and moderate knowledge of components of BPACR had statistically significant lower odds (OR:0.05 (95% CI: 0.02-0.13) and 0.10 (95% CI: 0.03-0.30) times, respectively) for greater practice of BPACR when compared to those with good knowledge. Respondents with poor knowledge of danger signs had statistically significant lower odds (OR: 0.08 (95% CI: 0.03-0.26) for greater practice of BPACR when compared to those with good knowledge. But predictive margins analyses demonstrates that knowledge, though critical to practice, is insufficient to optimize practice. The optimum number of danger signs women need to know to improve practice may be between eight to ten. Beyond this number, practice may not change significantly. Other predictors of BPACR practice include income level, parity, gravidity, and residential settings. The number of antenatal clinic visits had no statistically significant correlation with BPACR practice. Interventions to facilitate practice at the community level may be helpful to improve outcomes and bridge the know-do gap with respect to BPACR within the study context.