Background <p>This meta-analysis aims to assess the efficacy of behavioral therapy for selective mutism (SM) using the Selective Mutism Questionnaire (SMQ) and School Speech Questionnaire (SSQ).</p> Methods <p>We analyzed 12 articles involving 472 participants and comprising three randomized controlled trials and nine before-after or multiple baseline study designs.</p> Results <p>Our findings indicate a significant improvement in symptoms of SM, as indicated by the SMQ total, the SMQ subsections scores (school, home, and public), and the SSQ. The mean SMQ total score improved by 0.51 [95% confidence interval of 0.32–0.70] with a large effect size (Hedges’ adjusted g = 1.00 [0.62–1.39]). This effect did not differ significantly based on the study design. Based on the treatment strategy, web-based treatment demonstrated less improvement (0.12 [− 0.11–0.36]) compared with face-to-face treatment (0.59 [0.39–0.80]).</p> Conclusions <p>This meta-analysis revealed that SM treatment significantly improved their speaking behavior measured by the SMQ and SSQ, though potential subgroups that influence the treatment efficacy remain. SMQ has also shown validity and responsiveness as an outcome tool for behavioral therapy for SM. Further clinical practices with randomized controlled trials are recommended to clarify the potential differences of treatment or target populations.</p>