The primary purpose of this study is to elucidate the unclear patterns that have emerged in prior empirical studies investigating the relationship between TMT (Top Management Team) job-related diversity and firm performance, and to this end, a comprehensive investigation was conducted through meta-analysis. Furthermore, this study considered the influence of multidimensional contextual variables existing in the firm's internal and external environments (environmental dynamism, firm size, and average team tenure), specifically analyzing how these variables moderate (strengthen or weaken) the relationship between diversity and performance through quantitative and systematic methods. For the analysis, 42 relevant empirical studies (81 effect sizes and 13,478 teams) conducted and published over the past approximately 30 years from 1984 to 2013 were included in the sample. According to the analysis results, while TMT job-related diversity generally had a weak positive correlation with firm performance, this positive influence was doubled or tripled in highly dynamic environments and in relatively small firms. In contrast, in relatively stable environments and larger firms, the influence of diversity on firm performance was not prominently observed. Additionally, the positive effects of TMT diversity were found to be strengthened over time. Based on a more contingency-based perspective, the results of this study are expected to contribute to a more precise and systematic understanding of the mechanisms through which TMT diversity affects performance—specifically, understanding "when," "where," and "how" diversity influences firm performance.