Although algebraic reasoning has been considered as an important factor influencing students' mathematical performance, many students struggle to build concrete algebraic reasoning. Metacognitive training has been regarded as one effective method to develop students' algebraic reasoning; however, there are no published meta-analyses that include an examination of the effects of metacognitive training on students' algebraic reasoning. Therefore, the purpose of this meta-analysis was to examine the impact of metacognitive training on students' algebraic reasoning. Eighteen studies with 22 effect sizes were selected for inclusion in the present meta-analysis. In the process of the analysis, one study was determined as an outlier; therefore, another meta-analysis was reconstructed without the outlier to calculate more robust results. The findings indicated that the overall effect size without an outlier equaled d=0.973 with SE=0.196. Q=20.201 (p<0.05) and I[superscript 2] =0.997, which indicated heterogeneity of the studies. These results showed that the metacognitive training had a statistically significant positive impact on students' algebraic reasoning.