Sierra Leone has poor indicators of reproductive health and a high prevalence of unintended pregnancies. To date, no study has explored determinants of ovulatory cycle knowledge in Sierra Leone. We investigated geographic region to determine where the needs for improved ovulatory cycle knowledge are greatest in Sierra Leone. This is a cross-sectional study of women of reproductive age (n = 15,574) based on the 2019 Sierra Leone Demographic and Health Survey. Geographic region and sociodemographic covariates were included in a multivariate logistic regression model predicting the odds that participants possessed accurate knowledge of when in the ovulatory cycle pregnancy initiation is most likely. In Sierra Leone, 39.8% (CI = 37.4-40.9) of 15-49-year-old women had accurate knowledge of the ovulatory cycle. Women in the Northern and Southern regions possessed the highest prevalence of correct knowledge (46.7%, CI = 43.1-50.3 and 45.1%, CI = 41.9-48.2, respectively). Women from the Northwestern (AOR = 0.29, CI = 0.22-0.38), Eastern (AOR = 0.55, CI = 0.41-0.72), and Western regions (AOR = 0.63, CI = 0.50-0.80) had significantly lower odds of accurate ovulatory cycle knowledge compared to others. Women aged 15-19, those with a primary school education, and participants with a parity of none all had the lowest odds of correct ovulatory cycle knowledge as well. Less than four in ten women in Sierra Leone had accurate knowledge of when in the ovulatory cycle pregnancy is most likely to occur. This suggests that family planning outreach programs should include education on the ovulatory cycle and the importance of understanding the implications of its timing. This can reduce the risk of unintended pregnancies throughout Sierra Leone, and can have an especially positive impact in the Northwestern, Eastern, and Western regions, where ovulatory cycle knowledge was significantly lower.