Despite Northern Ireland's deeply rooted religious history and the assumption that its citizens' sexual attitudes and behaviours are more reserved than their English counterparts, comprehensive school-based relationships and sexuality education (RSE) has been statutory for primary and post-primary pupils since 2007. The non-biological aspects of the subject continue to remain non-statutory for all grade levels in England. This article presents a comparative analysis of the effect Northern Ireland's and England's policy-making models and networks have had on the status of sex and relationships education within each country's respective national curricula. Two main sets of issues are examined: the approaches taken and values upheld by policy actors, and access to "policy speak" and "power" within policy-making networks. Applying thematic and content analysis to official government transcripts, legislative and statutory policy texts and interview data, the article discusses connections among the main points of comparison and suggests that these central differences within Northern Ireland's and England's policy-making processes may explain what has been conducive to Northern Ireland's statutory comprehensive RSE policy development while comprehensive sex education remains controversial in England.