Objective: Two recent systematic reviews have surveyed the existing evidence for the effectiveness of active videogames in children/adolescents and in elderly people. In the present study, effect sizes were added to these systematic reviews, and meta-analyses were performed. Materials and Methods: All reviewed studies were considered for inclusion in the meta-analyses, but only studies were included that investigated the effectiveness of active videogames, used an experimental design, and used actual health outcomes as the outcome measures (body mass index for children/adolescents [k = 5] and functional balance for the elderly [k = 6]). Results: The average effect of active videogames in children and adolescents was small and nonsignificant: Hedges' g = 0.20 (95 percent confidence interval, -0.08 to 0.48). Limited heterogeneity was observed, and no moderator analyses were performed. For the effect of active videogames on functional balance in the elderly, the analyses revealed a medium-sized and significant effect of g = 0.68 (95 percent confidence interval, 0.13-1.24). For the elderly studies, substantial heterogeneity was observed. Moderator analyses showed that there were no significant effects of using a no-treatment control group versus an alternative treatment control group or of using games that were especially created for health-promotion purposes versus off-the-shelf games. Also, intervention duration and frequency, sample size, study quality, and dropout did not significantly moderate the effect of active videogames. Conclusions: The results of these meta-analyses provide preliminary evidence that active videogames can have positive effects on relevant outcome measures in children/adolescents and elderly individuals.