It is assumed that serious games influences learning in 2 ways, by changing cognitive processes and by affecting motivation. However, until now research has shown little evidence for these assumptions. We used meta-analytic techniques to investigate whether serious games are more effective in terms of learning and more motivating than conventional instruction methods (learning: k = 77, N = 5,547; motivation: k = 31, N = 2,216). Consistent with our hypotheses, serious games were found to be more effective in terms of learning (d = 0.29, p less than 0.01) and retention (d = 0.36, p less than 0.01), but they were not more motivating (d = 0.26, p greater than 0.05) than conventional instruction methods. Additional moderator analyses on the learning effects revealed that learners in serious games learned more, relative to those taught with conventional instruction methods, when the game was supplemented with other instruction methods, when multiple training sessions were involved, and when players worked in groups. (Contains 5 tables.)