Very little systematic research has been conducted on mentoring of youth with disabilities, especially science, technology, engineering, and mathematics (STEM) mentoring. This article describes findings from a qualitative study, conducted as a component of an explanatory, sequential mixed-methods investigation of the outcomes and processes of a STEM mentoring intervention for high school-aged youth with disabilities, provided by mentors with and without disabilities. Focus groups were conducted with 30 youth, 30 parents, and 28 mentors following their participation in a randomized trial of a mentoring intervention. Key themes include the benefits of mentoring for STEM career development, especially for older youth; the importance of relationship development, encouraging guidance, and participation in experiential activities; and personality and interest compatibility in successful mentor-mentee matching.