Right-wing extremist groups harness popular social media platforms to accrue and mobilize followers. In recent years, researchers have examined the various themes and narratives espoused by extremist groups in the United States and Europe, and how these themes and narratives are employed to mobilize their followings on social media. Little, however, is comparatively known about how such efforts unfold within and between right-wing extremist groups in Australia and Canada. In this study, we conducted a cross-national comparative analysis of over eight years of online content found on 59 Australian and Canadian right-wing group pages on Facebook. Here we assessed the level of active and passive user engagement with posts and identified certain themes and narratives that generated the most user engagement. Overall, a number of ideological and behavioral commonalities and differences emerged in regard to patterns of active and passive user engagement, and the character of three prevailing themes: methods of violence, and references to national and racial identities. The results highlight the influence of both the national and transnational context in negotiating which themes and narratives resonate with Australian and Canadian right-wing online communities, and the multi-dimensional nature of right-wing user engagement and social mobilization on social media.