As academics with practical experience of parliamentary service in Australia and Sweden, we take this opportunity to reflect on gender sensitisation drivers in these environments. By revisiting and comparing specific change processes in these two parliaments, we identify a previously missing driver of change, namely critical culture. We define this as an underlying institutional acceptance of the need for—and importance of—gender equality, socially, economically and politically. We suggest that critical culture is the foundation upon which other drivers of gender sensitive change—critical mass, critical acts and critical actors—work. We find that it is the confluence of mass, actors, acts and culture that achieves comprehensive gender sensitive reforms in parliaments. This has interesting implications for scholars and practitioners in the field of gender and parliament, a fairly young discipline that has not yet sufficiently conceptualised and empirically assessed the role of institutional culture despite a longstanding acknowledgement of its importance. We conclude by suggesting measures by which gender equality cultures could be strengthened in parliaments.