The Minimum Initial Services Package (MISP) for reproductive health has been the minimum standard for reproductive health service provision in humanitarian emergencies since 1995. Assessments of acute humanitarian settings in 2004 and 2005 revealed few MISP services in place and low knowledge of the MISP among humanitarian responders. Just 10 years later, assessments of humanitarian settings in 2013 and 2015 found largely consistent availability of MISP services and high awareness of the MISP as a standard among responders. We describe the multi-pronged strategy undertaken by the Women’s Refugee Commission and other Inter-agency Working Group on Reproductive Health in Crises (IAWG) member agencies to effect systemic improvements in the availability of the MISP at the onset of humanitarian responses. We find that investments in fact-finding missions, awareness-raising, capacity development, policy harmonisation, targeted funding, emergency risk management, and community resilience-building have been critical to facilitating a sea-change in reproductive health responses in acute, large-scale emergencies. Efforts were underpinned by collaborative, inter-agency partnerships in which organisations were committed to working together to achieve shared goals. The strategies, activities, and achievements contain valuable lessons for the health sector, including reproductive health, and other sectors seeking to better integrate emerging or marginalised issues into humanitarian action.