This meta-analysis examines the effectiveness of functional mathematics instruction, specifically purchasing skill instruction, for individuals with disabilities. Twenty-eight intervention studies were identified and reviewed. Because all studies employed single-subject research designs, a nonparametric procedure, the percentage of nonoverlapping data (PND), was used to estimate treatment effects. Results indicated a moderately positive effect for purchasing skill instruction (median PND = 87%). Maintenance (median PND = 100%) and generalization effects (median PND = 86%) revealed large and moderate effects, respectively. Further categorical comparisons indicated that variables such as participants' entry skills, money skill adaptations, type of purchase, error correction procedure, and instructional setting were related to the treatment effectiveness.