The purpose of this study is to determine the effect size of gender on motivation towards science learning by combining the results of studies, which were conducted to determine the effect of gender on motivation towards science learning, via the meta-analysis method. In this context, master's thesis, doctoral dissertations, and articles, which were conducted between 2010 and 2020, were suitable for the research problem, and had statistical data to be included in the meta-analysis study, were reviewed and examined in Turkish and English from national and international databases. As a result of the literature review, 2435 national and international studies were collected. Forty-nine studies, containing data suitable for coding protocol in accordance with the criteria determined by the researchers, were included in the meta-analysis. The sample size of 20.862 participants was obtained in the study (10.446 females and 10.416 males). The effect sizes and the combined effect sizes of the studies were calculated using "Comprehensive Meta-Analysis v 2.0 (CMA)." In the studies using the random effects model, the effect size of the gender variable on motivation towards science learning was determined to be 0.155 (95% CI, SE = 0.040). This value showed that the overall effect of the gender variable on motivation towards science learning was at an "insignificant" level in favor of the women. The results of the anova similarity analysis performed for the categorical moderators of publication type, scale type, and education level indicated that these moderators did not cause any statistically significant difference in the effect sizes. As a result of the meta-regression analysis performed for the publication year moderator -- which was evaluated as a continuous variable -- this moderator did not make any significant difference on the effect sizes of motivation towards science learning.