Design-based learning (DBL) offers opportunities to support students' content understanding. Previous DBL studies reported different effect sizes by using the data from one participant group. The goal of this study was to conduct a meta-analysis that would give a comprehensive picture of how DBL is connected to student achievement in different disciplines. In addition, we explored the moderators influencing achievement in DBL for K-12 education. After investigating contentrelated gains in our meta-analysis on 37 individual articles with 52 effect sizes, we found that DBL had a positive and large effect (g = 0.602) on achievement in K-12 education, and the effect size for science (g = 0.703) was higher than mathematics (g = 0.418) education. When considering the strong emphasis on science education in different DBL related frameworks and STEM (science, engineering, technology, and mathematics) education studies, this cumulative understanding could play an important role in the difference between science and mathematics. Studies that had control groups in the same school (g = 0.703) had statistically significantly higher effect sizes compared to studies that included control groups from different schools (g = 0.447). Studies with random assignment (g = 0.258) had statistically significantly smaller effect sizes compared to studies with non-random assignment (g = 0.623). In addition, the effect of DBL on