In this study, it is aimed to determine the effect of visualization on mathematics achievement in the thesis studies conducted in Turkey. In this context, the findings obtained from individual studies are combined via meta-analysis. For this purpose, Council of Higher Education (CoHE) National Thesis Center database was thoroughly scanned by using keywords. A total of 35 thesis studies, 26 of which are master's thesis and 9 of which are doctoral dissertations were reached as a result of the scanning performed. 34 theses are included in the meta-analysis in line with their inclusion criteria and 42 effect sizes were calculated pertaining to these thesis. To examine the normal distribution of effect sizes and to perform other analyses, statistical programs of MetaWin and Comprehensive Meta-Analysis (CMA) were used respectively in the study. In the calculation of effect sizes, quantities of studies included in meta-analysis Hedges's g was used and confidence level in calculations of effect sizes was taken as 95%. The average effect size value calculated in accordance with random effect model was found as 0.811 with the standard error of 0.076. Positivity of effect size shows that the implication effect is in favour of the experimental group. Basing on this, it can be said that visualization has a moderate effect on mathematics achievement.