This meta-analysis was conducted to systematically synthesize research findings on effects of gamification on cognitive, motivational, and behavioral learning outcomes. Results from random effects models showed significant small effects of gamification on cognitive (g = .49, 95% CI [0.30, 0.69], k = 19, N = 1686), motivational (g = .36, 95% CI [0.18, 0.54], k = 16, N = 2246), and behavioral learning outcomes (g = .25, 95% CI [0.04, 0.46], k = 9, N = 951). Whereas the effect of gamification on cognitive learning outcomes was stable in a subsplit analysis of studies employing high methodological rigor, effects on motivational and behavioral outcomes were less stable. Given the heterogeneity of effect sizes, moderator analyses were conducted to examine inclusion of game fiction, social interaction, learning arrangement of the comparison group, as well as situational, contextual, and methodological moderators, namely, period of time, research context, randomization, design, and instruments. Inclusion of game fiction and social interaction were significant moderators of the effect of gamification on behavioral learning outcomes. Inclusion of game fiction and combining competition with collaboration were particularly effective within gamification for fostering behavioral learning outcomes. Results of the subsplit analysis indicated that effects of competition augmented with collaboration might also be valid for motivational learning outcomes. The results suggest that gamification as it is currently operationalized in empirical studies is an effective method for instruction, even though factors contributing to successful gamification are still somewhat unresolved, especially for cognitive learning outcomes.