The goal of this study was to examine the effects of behavioral sleep extension interventions on sleep duration outcomes in children and adults ≥ age 12. We conducted a systematic literature review, article extraction and meta-analysis. Our search yielded 42 studies from 14 countries. The majority of studies (n = 19) enrolled adults, 10 studies enrolled college students, 13 enrolled children (high school or middle school aged). Results from the meta-analysis demonstrated behavioral sleep extension resulted in a significantly higher sleep duration as compared to control group or baseline, with pooled standardized mean difference (SMD) that was similar for both two-arm 0.80 (95 % CI 0.28 to 1.31; p < 0.01;   = 99.2%) and one-arm studies 0.75 (95% CI 0.39 to 1.11; p < 0.01;   = 86%), and there was significant heterogeneity among both study types. Subgroup analyses revealed that studies with direct interventions on sleep duration (i.e., specified the sleep schedule) had larger effects compared to indirect methods (coaching, educational approaches) and a greater number of curriculum components was associated with smaller effects. Results of this review demonstrate that sleep extension studies are effective at extending sleep in a variety of populations but improving the description of intervention methods and use of more rigorous study designs will improve the quality and reproducibility of this area of research.