This case study is the culmination of a three-year initiative in Samburu and Turkana counties in Kenya to advance understanding of how to strengthen adolescent- and gender- responsive health systems. The report summarizes the processes, results, and lessons learned of the initiative and argues that employing an adolescent- and gender-responsive approach to health systems, facilitated by a novel assessment tool, is feasible and has the potential to drive improvements within subnational health systems. The case study outlines recommendations on how to apply an adolescent- and gender-responsive health systems approach to more sustainably improve adolescents’ and youth’s access to and use of quality health and nutrition services at scale.