Research on adolescent aloneness and well-being yielded mixed results and adolescents’ specific motivations for spending time alone remain underexamined from a qualitative perspective. High-ability adolescents have been proposed to experience a greater affinity for aloneness than typical adolescents, yet empirical evidence on this differential need and specific motivations for time spent alone is lacking. This mixed-method study examined motivations underlying time spent alone, their relations to psychosocial well-being, and differences between high-ability and typical adolescents in a matched sample. The sample consisted of 540 adolescents (Mage = 16.25 years, SDage = 0.39, age range = 13.3–17.9 years, 42% female), with 270 adolescents identified as high-ability (MIQ = 128) and 270 typical adolescents (MIQ = 104). Both positive and negative motivations for time spent alone emerged, with only negative motivations being associated with poorer psychosocial well-being. Compared to typical adolescents, high-ability adolescents reported a stronger affinity for aloneness and more often cited one negative motivation for spending time alone, that is, feeling unable to be themselves around others. These findings underscore the need to identify and provide targeted support to high-ability students who isolate themselves due to social misfit.