Objective: Behavioral rating scales are widely used assessment measures for attention-deficit/hyperactivity disorder (ADHD; Handler & DuPaul, 2005).The objective of this review was to examine the ecological validity of commonly used ADHD rating scales. Data Selection: Apa PsycInfo, EBSCOHost (Medline), PsycArticle, Sage Journal, and Science Direct databases were searched. Inclusion criteria included peer-reviewed articles, written in English and included (1) participants diagnosed with ADHD, under age 18, and no other neurodevelopmental disorders; (2) blinded classroom observation rating made by trained observers; (3) rating scales completed by teacher and parent; (4) studies included in meta-analysis included Pearson’s r between classroom observations and rating scales. Data Synthesis: Data was selected and extracted by two reviewers, based on PRISMA guidelines (Gates & March, 2016). The combined search yielded 1052 potentially eligible papers. Eleven studies met all criteria for review, and three studies were retained and included in the meta-analysis, comprising ratings for 516 children and adolescents. Meta-analysis used a random-effects model found the combined effect size of all studies of r = 0.2005 (p < 0.001). Additional analysis of heterogeneity found low heterogeneity in the three studies (I2 = 36.27%; Q(df = 15) = 21.5921, p = 0.1190; T2 = 0.0035 (SE = 0.0035)). Conclusions: Our meta-analysis provides evidence in support of the ecological validity of several commonly used behavioral rating scales. More research with multi-informant data, including clinician observations, is needed to further understand the ecological validity of behavioral rating scales when assessing ADHD symptoms.