There are differences in the stock returns of cellular operator companies listed on IDX and previous research on the influence of fundamental factors on stock returns of mobile operator companies has not included the presence of COVID 19 pandemic that entered Indonesia in early 2020. Therefore, the purpose of this research is to analyze, evaluate, and understand the influence of external fundamental factors such as macroeconomic factors and market returns and internal fundamental factors such as financial ratios to the stock return of mobile operator company listed in IDX period 2012 to 2021 with the COVID 19 pandemic as a moderating variable. The variable used in this study are GDP growth (GDP), exchange rate (ER), market return (MR), return on equity (ROE), net profit margin (NPM), current ratio (CR), total asset turnover (TATO), debt-to-equity ratio (DER), and COVID 19 as independent variables. This study uses company stock returns as an independent variable and COVID 19 as a moderating variable. This study used a quantitative approach. The methodology being used was panel data regression using the common effect model (CEM), through 160 observations. The results of this study were partially MR and ROE has a positive and significant effect on the companies' stock returns. The COVID 19 pandemic moderates the effect of ER on the companies' stock returns. Simultaneously GDP, ER, MR, ROE, NPM, CR, TATO, DER, and COVID 19 affected the companies' stock return. The results of this study support the efficient market hypothesis theory that stock prices reflect all the information contained in it including fundamental information. Furthermore, the results of this study can be used as a reference for investors and management who run the cellular operator company. They must pay attention to MR and ROE as well as COVID 19 which moderates the effect of ER on stock returns.