Although peer-mediated interventions have emerged as an evidence-based practice for students with autism spectrum disorder (ASD), little attention has focused on approaches for tailoring these interventions to meet individual students' unique needs. In this systematic literature review of 29 studies, we identified assessment procedures used to inform peer-mediated social interventions for students with ASD. Few studies included well-described assessment methods. While direct observations often were used to tailor social outcomes, weaker methods were used to individualize intervention components. Furthermore, the focus of most assessment procedures was narrow, addressing only one feature of the intervention or outcome. Results of this review highlight the need to improve assessment reporting, use more rigorous assessment methods, and further evaluate the effectiveness of assessments to individualize peer-mediated interventions.