BackgroundSierra Leone is a religiously diverse country, with Christianity and Islam being the dominant faiths. This religious landscape plays a significant role in shaping attitudes towards family planning and contraceptives. We examined religious leaders’ knowledge of family planning and modern contraceptive methods.MethodsIn September 2021, data was collected from 116 religious leaders in Sierra Leone, including 32 Muslims and 84 Christians from nine different denominations from sixteen districts, through 16 focus group discussions. The data was subjected to a thematic analysis using NVIVO 12 software.ResultsThe study found a spectrum of opinions among religious leaders, both between religions (Christianity vs. Islam) and within denominations of Christianity. There was a general acceptance of natural birth spacing methods, like abstinence during fertile periods, across both Christian and Muslim leaders. Views on modern contraceptives were more divided. Catholics generally opposed them, citing religious doctrines against interfering with procreation. Pentecostals and some Muslims, however, found them permissible under certain circumstances, like promoting family well-being or spacing births for health reasons.ConclusionThe study reveals that religious leaders’ views on family planning in Sierra Leone are multifaceted. Understanding these nuances is crucial for designing effective family planning programs. By working with denominations that are more accepting of modern methods and leveraging the support for natural birth spacing methods across religions, there’s potential to improve reproductive health outcomes in Sierra Leone.