This article reports a meta-analysis of energy expenditure (EE) of playing active video games (AVGs). In particular, heart rate (HR), oxygen consumption (VO2), and EE were assessed and three moderators for the effects of AVGs--types of AVG, player age, and player weight status--were analyzed. The results show that playing AVGs significantly increased HR, VO2, and EE from resting. The effect sizes of playing AVGs on HR, VO2, and EE were similar to traditional physical activities. AVG type and player age were significant moderators for the effects of AVGs. The finding suggests that AVGs are effective technologies that may facilitate light- to moderate-intensity physical activity promotion.