Purpose: The development of vocabulary size in deaf/hard of hearing (DHH) children and adolescents can be delayed compared to their peers due to lack of access to early language input. Complementary vocabulary interventions are reported in the literature. Our aim is to evaluate the effectiveness of intervention methods for their vocabulary improvement. Method: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we searched five databases for peer-reviewed journal articles in English, published between 2000 and 2022 (inclusive), reporting vocabulary interventions for 2- to 18-year-old DHH children and adolescents without comorbidities. We conducted separate meta-analyses using a random-effects model on receptive oral vocabulary, expressive oral vocabulary, and signed vocabulary. We assessed the methodological quality of each paper. This review is preregistered in PROSPERO (International Prospective Register of Systematic Reviews) with ID CRD42021243479. Results: We included 25 group studies in this review out of 1,724 identified records. The quality assessment of the studies revealed risk of bias ranging from some concerns to high risk. Experimental vocabulary instruction produced improvement in receptive oral vocabulary (Hedges's g = 1.08, 95% CI [0.25, 1.90], I[superscript 2] = 93.46, p = .01), expressive oral vocabulary (Hedges's g = 1.00, 95% CI [0.18, 1.83], I[superscript 2] = 96.37, p = .02), and signed vocabulary (Hedges's g = 1.88, 95% CI [1.09, 2.66], I[superscript 2] = 96.01, p < .001) in the experimental groups. Written vocabulary and general vocabulary skills are also reported as a synthesis of results. Conclusions: Multisensory and multimodal explicit vocabulary instruction for DHH children and adolescents is helpful in improving vocabulary acquisition with respect to baseline levels. However, its effectiveness must be carefully interpreted due to the lack of proper control groups and details on "treatment as usual" reported in the studies.