Uncertainties are important factors that influence the decisions made by societies. Economic uncertainties closely affect society’s consumption and investment behaviour. Rising stock markets increase investors’ confidence, resulting in more purchases and higher stock prices and, in this context, an increase in consumer spending. When stock prices decrease, company investments are also negatively affected as consumer spending declines. Thus, increases and decreases in stock prices affect the general economy as they affect business confidence and consumers. The study analyses the effect of uncertainty in economic policies on stock markets, leading to a decrease in investor confidence in the economy. Such effects in G7 countries were examined using the nonlinear autoregressive distributed lag (ARDL) model for the period 1998:M05–2020:M09. This method was able to capture symmetries and asymmetries in the relationship between economic policy uncertainties and the stock markets. The results showed that heightened uncertainty in economic policy in Japan has a significantly negative effect on the stock market index, but in Germany and Italy, it has a significantly positive effect. Rising interest rates have negatively affected the stock market index in the United States, Canada, Japan, Italy, and the United Kingdom. The increase in the industrial production index is positively related to the stock market index in the United States, Canada, Japan, Italy, and France. Additionally, uncertainties in economic policy have asymmetric impacts on the stock market index in the United States, Canada, Japan and Italy, and symmetrical impacts in Germany, France and the United Kingdom.