Purpose: The aims of this systematic review are to (a) synthesize the literature on interventions targeting expressive communication in adults with autism spectrum disorder and (b) evaluate the effectiveness of the interventions. Method: The literature search resulted in 7,196 articles. The research team used 2 reviewers and consensus for title/abstract review, full-text review, and quality review. To be included, studies had to (a) include at least 1 adult (18 years of age and above) with an autism spectrum disorder; (b) examine an intervention, treatment, or model of care; (c) provide outcome data related to expressive communication modalities/domains; (d) be experimental or quasi-experimental; and (e) be published in English. Twenty-two studies (14 single-case design and 8 group design), with a total of 256 participants and varied interventions and outcome variables, met criteria for inclusion. Effect sizes are presented for group design studies, and visual analysis results are outlined for single-case design studies. Results: Examination of treatment effects in the included studies showed positive effects, overall; however, there was great variability between studies. Single-case design studies showed evidence of functional relations in all but 1 study, with most showing medium to large effects, as well as maintenance and generalization of gains. Group design studies showed a wide range of effects from near-zero to large effects. Differences in intervention strategies and durations, as well as in participant characteristics and outcome measures, presented barriers to aggregation. Conclusions: This review highlights the need for increased high-quality research examining interventions targeting expressive communication in adults with autism spectrum disorder and also pinpoints interventions with potential for future study and use in this population.