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.