We assessed the decisional capacity (DC) of 72 youth with HIV, ages 13-24, using the MacArthur Competence Tool for Treatment, a structured interview that assesses DC along the following dimensions: understanding, appreciation, reasoning, and the ability to express a choice. Using previously established cutoff scores, results suggested 100% of youth were competent in the area of appreciation, but only 62% and 60% were competent in the areas of understanding and reasoning, respectively. Additional descriptive analyses reveal more detailed information regarding specific strengths and weaknesses within each of the dimensions of decisional capacity. These findings have important implications for health literacy initiatives, medical education, and treatment for youth with HIV, and support the need for adherence and secondary prevention interventions that include a decisional capacity component.