Background: Continuous positive airway pressure (CPAP) therapy is the treatment of choice for Obstructive Sleep Apnea (OSA) syndrome; however, interventions to improve CPAP adherence are still inconclusive. Objective: This study aimed to examine the effectiveness of behavioral and psychosocial interventions on CPAP adherence. Methods: The PRISMA guidelines and JBI approach for Systematic Review and Meta-analysis were used. Participants included 1) newly diagnosed patients with OSA, naive to CPAP treatment; 2) any type of behavioral and/or psychosocial intervention delivered via individual or group level; 3) CPAP adherence as an outcome. Two reviewers independently selected studies, evaluated their methodological quality, and extracted data. Results: Critical appraisal was conducted on 34 of the 1657 studies, with 18 RCTs included in the final review. Telemonitoring increased the mean nightly hour of CPAP use compared to standard care (WMD = 0.76, 95 % CI = 0.31-1.20, p = 0.001, I2 = 0 %, moderate certainty of evidence). Positive results were discovered in Motivational Enhancement Therapy (MET) (WMD = 1.22, 95 % CI = 0.28-2.16, p = 0.011, I2 = 65 %, very low degree of certainty of evidence). The combined effects of cognitive therapy and education on CPAP adherence were inconclusive. Behavioral/supportive interventions improved mean nightly CPAP use in both the short term (WMD = 1.49, 95 % CI = 0.16-2.81, p = 0.029, I2 = 30 %, very low certainty of evidence) and long-term follow-up (WMD = 1.67, 95 % CI = 1.55-1.79, p = 0, I2 = 0 %, very low certainty of evidence). Conclusions: Telemonitoring improved the mean nightly hour of CPAP utilization compared with standard care. Motivational Enhancement Therapy (MET) had the most significant effect on long-term adherence.