Chronic medical conditions persist for one year or more, require ongoing medical intervention, and impair functioning. Approximately 10-30% of youth are diagnosed with a chronic medical condition. Youth with chronic medical conditions are at heightened risk for psychiatric comorbidity and negative health outcomes across the lifespan. Managing a chronic medical condition becomes particularly difficult during the adolescent developmental period, which is marked by changes in biological, psychological, social, and cognitive development. Assessment and intervention with adolescents is often challenging, as this is a period of transition and risk. Given increasing rates of chronic medical conditions, health service psychologists are likely to encounter youth with medical conditions in their clinical practice. In this paper, an overview of chronic medical conditions and adolescent development is provided and fundamental assessment and treatment components, including multicultural considerations, are explored.