There has been a long search for cognitive assessments that reveal aptitudes thought to be useful for treatment planning. In this regard, since the 1990s, there has been some enthusiasm for the Cognitive Assessment System (CAS) and its potential promise for informing treatment due to its alignment of theory, assessment instrument, and suite of interventions. The purpose of this meta-analytic review was to synthesize research pertinent to the treatment utility of the CAS according to a taxonomy of treatment utility. A total of 252 articles were produced by an electronic search and eligibility screening yielded 16 articles meeting criteria for consideration. Most studies described in these articles utilized obtained difference designs, focused on the Planning composite scores from the CAS, and addressed math interventions. Only seven studies with publication dates from 1995 to 2010 yielded sufficient information to be included in the meta-analysis. A random effects model was employed to determine the overall treatment utility effect across 114 participants apportioned to 14 groups and comprising eight comparisons. Results yielded an overall moderate effect size (0.64, 95% CI [0.24, 1.03], p = .002), but it was associated with significant imprecision (due to a low number of viable studies and small sample sizes across most studies) that prohibits reliable conclusions from being drawn. Assessment of between-study heterogeneity and moderator analysis was not possible. Considering these findings, additional research is needed to support the treatment utility of the CAS—even after more than 27 years of study. Furthermore, there are no published studies regarding the treatment utility of the second edition of the CAS, which was published in 2014. These results suggest that there is insufficient empirical grounding to enable practitioners to use this instrument to develop effective treatments for reading, mathematics, or writing. More direct interventions designed to enhance academic skill development should be employed.