Given the widespread use of school-based problem-solving teams (SB PSTs), empirical evidence establishing their effectiveness is essential. Guided by the "Input-Mediator-Output-Input" (IMOI) Framework, this meta-analysis examined SB PST effectiveness generally and differentiated measured effects by targeted outcomes and specific SB PST processes used. Data from 13 studies (14 effects) yielded a large overall weighted estimate of effect (g = 0.84). Measured SB PST effects on student outcomes (e.g. academic or behavioral improvement) appeared large (g = 0.89), on systems outcomes (i.e., reduction in referrals to special education) were moderate (g = 0.66), and on team outcomes (i.e., procedural fidelity) appeared large (g = 1.00). Although not a significant moderator of effect, team use of an evidence-based process was associated with larger effects (g = 1.78, k = 8). Similarly, although non-significant, studies that met rigorous, published standards for research methods showed larger outcome effects (g = 1.10, k = 2).