Psychological interventions for sleep-wake disorders have medium-to-large effect sizes, however whether behavioral randomized controlled trials (RCTs) targeted underserved populations or addressed contextual and cultural factors is unknown. We conducted a systematic review to: (a) examine sociodemographic characteristics of behavioral RCTs for prevalent sleep-wake disorders and sleep disturbances that targeted undeserved adults, (b) identify types of cultural adaptations (surface-level, deep-level), and (c) describe intervention effectiveness on primary sleep outcomes. Overall, 6.97% of RCTs (56 studies) targeted underserved groups (veterans, women, racial/ethnic minorities, low socioeconomic status, disability status); 64.29% made surface-level and/or deep-level cultural adaptations. There was a lack of racial/ethnic, socioeconomic, sexual orientation, and linguistic diversity. Most cultural adaptations were made to behavioral therapies, and cognitive behavioral therapy for insomnia (CBT-I). Surface-level cultural adaptations to the delivery modality and setting were most common. Deep-level cultural adaptations of the content and core intervention components were also typical. Intervention effectiveness varied by type of adapted intervention and participant population. RCTs of adapted CBT-I interventions among participants with a definite sleep disorder or sleep disturbance showed consistent significant reductions in adverse sleep outcomes versus control. These findings have important implications for the use of cultural adaptations to address behavioral sleep medicine disparities.