The increasing dominance of domestic investors and the rising concentration of market capitalization in conglomerate-affiliated firms have raised questions regarding their role in shaping stock market performance in Indonesia. Despite this structural shift, empirical studies have largely focused on foreign capital flows and have rarely distinguished domestic investor activity between conglomerate and non-conglomerate stocks. This study aims to obtain and analyze empirical evidence on the effect of domestic investor fund flows into conglomerate and non- conglomerate stocks, as well as selected macroeconomic and financial market indicators, on the return ratio of the IHSG. This study employs a quantitative approach using monthly time-series data from January 2009 to December 2025, consisting of 204 observations. The model is estimated using ordinary least squares. Since White’s heteroscedasticity test indicates the presence of heteroscedasticity, the final statistical inference is based on White heteroscedasticity-consistent robust standard errors using the Huber-White-Hinkley covariance method. The results show that domestic investor fund flows into conglomerate stocks have a negative but statistically insignificant relationship with return ratio of IHSG. Meanwhile, domestic investor fund flows into non-conglomerate stocks have a negative and statistically significant relationship with IHSG returns. In addition, increases in the Indonesian 10-year government bond yield and rupiah depreciation against the US dollar are found to have significant negative relationships with return ratio of IHSG, while gold price returns do not show a statistically significant relationship. These findings suggest that domestic investor activity, particularly in non-conglomerate stocks, and macroeconomic conditions play an important role in explaining stock market dynamics in Indonesia.