The HIV/AIDS pandemic continues to be a significant global public health crisis. The main HIV/AIDS treatment is the antiretroviral therapy (ART), which is highly effective but depends on the patient's adherence to be successful. However, the adherence to antiretroviral therapy remains unsatisfactory across different populations, which raises considerable difficulties at both individual and collective levels. Suboptimal adherence to ART can be overcome through multidisciplinary management that includes evidence-based psychosocial interventions. Existing reviews on these interventions have focused mainly on studies with experimental designs, overlooking valuable interventions whose evidence comes from different study designs. Here, we aimed to carry out a comprehensive review of the current research on psychosocial interventions for ART adherence and their characteristics including studies with different designs. We conducted a systematic review following PRISMA guidelines. We searched five databases (Pubmed, EBSCO, LILACS, WoS and SCIELO) for articles reporting a psychosocial intervention to improve treatment adherence for people living with HIV (adults). The quality of each study was analyzed with standardized tools, and data were summarized using a narrative synthesis method. Twenty-three articles were identified for inclusion, and they demonstrated good to fair quality. Individual counseling was the most frequent intervention, followed by SMS reminders, education, and group support. Most interventions combined different strategies and self-efficacy was the most common underlying theoretical framework. This review provides insight into the main characteristics of current psychosocial interventions designed to improve ART treatment adherence. PROSPERO number: CRD42021252449.