Background <p>Gamification of learning has been regarded as an important pedagogy to promote students’ learning outcomes, and attempts have been made to integrate it into STEM education. However, the influence of gamification of learning on K-12 students’ STEM educational outcomes, such as domain knowledge, higher-order thinking, and affective outcomes, remains under-researched.</p> Objective <p>This study aims to investigate strategies for integrating gamified learning in STEM education, examine its effects on domain knowledge, higher-order thinking, and affective outcomes, and explore K-12 students’ perceived benefits and challenges of implementing gamified learning in STEM education.</p> Methods <p>We systematically reviewed 86 empirical studies involving 7,128 participants from leading bibliographic databases, examined the effects of gamified learning in STEM using a meta-analysis, and investigated the benefits and challenges of implementing gamified learning in STEM education using a qualitative synthesis.</p> Results <p>Our findings revealed medium to large effect sizes in favour of gamified learning on domain knowledge (Hedges’ <i>g</i> = .823; <i>p</i> &lt; .001), higher-order thinking (Hedges’ <i>g</i> = .880; <i>p</i> &lt; .001), and affective outcomes (Hedges’ <i>g</i> = .577; <i>p</i> &lt; .001) using a random-effects model. The thematic analysis of interview data from 26 articles identified three themes with 15 sub-themes of benefits and three themes with six sub-themes of challenges of implementing gamified learning in STEM education.</p> Conclusions <p>This review synthesized findings on the impact of gamified learning across STEM learning outcomes and various moderating factors, while also providing rich insights into authentic participant perceptions of its application in STEM education. This study yielded pedagogical and theoretical insights to effectively implement gamified learning in STEM education.</p>