I examined the stock market response to the regulation of non-financial disclosure of listed firms in EGX, specifically regarding its implications on the information asymmetry and stock price crash risk. Employing an event study, I used two natural events in the Egyptian context to measure the stock market response to the regulation of non-financial disclosure. By using a sample of firms listed in EGX-100 during 2012-2018, results indicated that there is no significant effect of the regulation of non-financial disclosure -that aimed to enhance the reliability of non-financial disclosure -on the information asymmetry, but they documented a negtaive significant effect of the regulation of non-financial disclosure -that aimed to enhance the readability and the comparability of non-financial disclosure -on the information asymmetry. These also documented an adverse effect of the regulation of non-financial disclosure on firms' stock price crash risk. However, the results suggested that the effect of the regulation of non-financial disclosure on firms' stock price crash risk, is not mainly due to its effect on the information environment, but it can be interpreted by its effect on the management incentives to manipulate information or conceal bad news.