This study employed a small-scale qualitative approach to examine how the Emotional Literacy Support Assistant (ELSA) programme operates in secondary schools, focusing on facilitating factors and challenges in its implementation. Research on ELSA interventions in secondary schools is limited; this study seeks to address this gap and provide insights to inform its implementation in these settings. A multiple case study design and semi-structured interviews were conducted in two secondary schools in one South England Local Authority with 14 participants, including ELSAs, Special Educational Needs Coordinators, pupils, and school staff. Cross-case thematic analysis identified four overarching themes: 'ELSA programme links with wider systems'; 'a structured and flexible intervention'; 'core ELSA skills and qualities'; and 'challenges for ELSAs and pupils'. These findings contribute to understanding ELSA programme implementation in secondary schools and have implications for enhancing its effectiveness and impact.