Purpose: The main aim of the systematic review and meta-analysis was to evaluate the effectiveness of language interventions for school-aged children who are d/Deaf and hard of hearing (DHH). We focused on studies targeting meaning-based aspects of language, such as vocabulary, grammar, and narrative skills. We included randomized controlled trials and quasi-experiments with a control group and a pre-post design. A secondary aim was to describe the characteristics of effective interventions identified in the systematic review. Method: The review was preregistered in PROSPERO (ID CRD42021236085). We searched 10 academic databases for peer-reviewed journal articles reporting language interventions for children who are DHH aged 6-12 years. We assessed the quality of included studies using Critical Appraisal Skills Programme checklists. A meta-analysis was conducted on the overall effect of interventions. In addition, we calculated separate effect sizes for vocabulary and morphosyntactic knowledge. Results: We identified 14 studies totaling 794 children. Quality assessment revealed concerns of risk of bias in most studies because study characteristics were not comprehensively reported. The meta-analyses of language interventions revealed a large main effect of g = 0.79. Subdomain analyses revealed similar effects for morphosyntactic knowledge g = 0.81 and vocabulary g = 0.71. Conclusions: Few high-quality studies examine the effects of language interventions for children who are DHH. However, the studies that exist reveal robust effects, especially for morphosyntactic abilities. Intervention approaches were diverse, and the largest intervention effects were found in studies with a randomized controlled design and near-transfer outcome measures closely aligned with the intervention content. Future studies should adhere to established guidelines for reporting results from controlled experimental study designs.