Given the importance of estimating stock returns, the purpose of this study was to identify the factors affecting stock returns by using the meta-analysis method. Meta-analysis is the main tool for combining results in social and behavioral research. It allows researchers to combine quantitative results of studies, explain the compatibility of results, and achieve a single result. Based on the research background, the impacts of different factors on stock returns were considered. A model of factors affecting stock return is designed in the analysis of empirical studies. This research used the meta-analysis method to comprehensively examine the factors affecting stock returns and assess the different factors that had been examined in various studies over the past years. In a similar research, the researcher had selected the factors affecting stock returns and only tested the selected factors via general categories. However, in this research, a more comprehensive study was conducted to separately examine all the factors whose effects on stock returns had been tested in different studies. Therefore, some of the factors investigated in this research had not been studied in the previous research. Accordingly, a model of factors affecting stock returns was developed. In this research, 422 studies were collected and 102 of them were analyzed. Totally, 153 factors were extracted from these studies and finally, 16 factors were tested. The type of effect size calculated in this study was r. Among the examined factors, earnings per share, operating cash flow, net operating assets, operating earnings, market return, earnings quality, and return on equity had an impact on stock returns. Since the majority of the factors affecting stock returns were related to the financial reports of companies, i.e., their financial status and performance, those factors could be considered to investigate investment opportunities.Keywords: Stock Return, Financial Investment, Fundamental Variables, Financial Ratios, Meta-analysis. IntroductionThe stock return is considered as one of the most important criteria in financial decisions. So far, many studies have been conducted to predict stock returns and provide a comprehensive and reliable model for investors and financial activists. The Capital Asset Pricing Model (CAPM) is one of the most important models in the financial field, especially for estimating stock returns (Murthy et al., 2017; Graham & Harvey, 2001). Although the experimental tests initially confirmed the predictive power of this model regarding the positive linear relationship between systematic risk and stock returns, the results of recent studies indicated that the beta coefficient alone had the power to explain the differences in average stock returns, while other variables were also effective in explaining the differences in stock returns (Fama & French, 1992). Despite examining the effects of various factors, combining the results and presenting a comprehensive model of the factors affecting the stock return, have always been of interest. Meta-analysis methodology, which is the main tool for combining results in social and behavioral research, allows researchers to combine quantitative results of studies (Asgarnezhad Nouri et al., 2016). Therefore, the purpose of this meta-analysis was to expand the pattern of factors affecting the stock returns. Method and DataIn this research, the meta-analysis method was used to comprehensively examine the factors affecting stock returns, as well as the different factors that had been examined in various studies over the past years. In this meta-analysis, 422 studies were collected and 102 of them were analyzed. Totally 153 factors were extracted from these studies and finally, 16 factors were tested. The r effect size was used as the effect size measure, which was calculated following Cohen (1977), Card (2015), and Rosenthal and DiMatteo (2001). FindingsAt the significance level of 1%, the heterogeneity of the effect size of the studies was confirmed. As a result, due to the heterogeneity of the effect size, the model of random effects was used. In addition, the value of the I2 statistic for all the factors was greater than 70, which showed that the heterogeneity of the effect size of the studies was at a high level. In general, among the investigated factors, earnings per share, operating cash flow, net operating assets, operating earnings, market return, earnings quality, and return on equity had an impact on the stock returns. The results of the methods of evaluating publication bias also showed that there was no significant bias in this meta-analysis ContributionIn similar meta-analyses, the researcher had selected the factors affecting stock returns and only tested the selected factors in general categories, while in this research, all the factors whose effects on stock returns had been tested in different studies were separately examined in a more comprehensive study to develop a pattern of factors affecting stock returns. In this meta-analysis, the effects of earnings-to-sales ratio, earnings per share, operating earnings, return on assets, earnings quality, and economic added value on stock returns were investigated, while these factors had not been investigated in similar meta-analyzes. The results showed the positive impact of earnings per share, operating earnings, and earnings quality on stock returns among these factors. Conclusion According to the research results, investors and capital market participants are suggested to pay attention to the variable of earnings per share as one of the influencing factors on the stock market for predicting stock returns. The earnings per share represents the company’s performance in terms of profitability. It is part of the variables of fundamental analysis based on the analytical approach. Among other factors affecting stock returns, we could mention operating cash flow and net operating assets. Therefore, to choose stocks for investment, investors are suggested to examine the company's operations and specifically the items related to the company's cash flow and net operating assets. Market returns were among other factors that affect stock returns. Therefore, it is suggested that investors pay attention to changes in the market yield to estimate the changes in the share value. Based on the research findings, the earnings quality was another factor affecting stock returns. Continuity and reproducibility of earnings, transparency and growing earnings, reflection of the economic reality of the company, etc. were the issues raised about the earnings quality. Hence, the investors are suggested to pay attention to it when examining different stocks. Also, among the financial ratios examined in this research, the return on equity had an impact on the stock return. Therefore, investors are suggested to pay attention to the ratio that is focused on the company's net earnings and shareholders' equity to choose stocks and check their value changes. In general, since the majority of the factors affecting stock returns based on this research were related to the company's financial reports, i.e, the company's financial status and performance, these factors can be considered to investigate investment opportunities.