The present article attempts to reinterpret the findings of most recent studies investigating effect of using games for teaching purposes. A methodological approach combining a meta-analysis of quantitative data with qualitative ones was adopted in order to present the broadest picture of the current research on educational use of games. To this end, we conducted a meta-analysis of 180 effect size comparisons out of 154 empirical studies on the effect of both digital and non-digital games on academic achievement conducted during the period from 2004 to 2019 in order to determine the overall effect size of using games for teaching various subjects. The overall sample size of the studies included a total number of 12800 participants. Some moderator analyses were also carried out to determine the exact efficiency of educational games in terms of student levels, durations of implementation of game activities, school subjects in which games were used, class sizes, kinds of games and achievement tests used. The findings suggest that educational games have a positive effect on academic achievement and this effect is at a medium level (g = 0.695). The highest effect sizes were observed in foreign language courses (g = 0.87), small (less than 50) class sizes (g = 0.87), and in non-digital games (g = 0.90). Moreover, we conducted a meta-thematic analysis based on document analysis of qualitative studies in order to further consolidate the findings of the meta-analysis. The meta-thematic dimension of our study reveals cognitive contributions as well as drawbacks of game-based teaching, and provides suggestions for conducting educational games in a better way.