This article is a summary of FHI 360’s Strengthening HIV/AIDS Services for Key Populations in Papua New Guinea project. From 2012 to 2018, FHI 360 developed training programs and tools to strengthen the capacity of local agencies to provide key populations with prevention, care and support for HIV and gender-based violence. The project team learned valuable lessons for future programs that included the need for consistent adaptation of interventions toward key populations and communities.