It has been nine years since the Indonesia Stock Exchange established a system called Syariah Online Trading System (SOTS), but the number of investors using this system is still relatively small compared to the regular investor. Moreover, the number is much smaller if it is compared to the potential number of sharia financial markets. This study aims to describe the behavior of Muslim investors in Indonesia who use the regular stock account instead of the sharia account. We surveyed by using both offline and online questionnaires, whereby the investors were asked to compose the imaginary stock portfolios consisting of stocks and their weights. Using a convenience sampling method, we succeeded in interviewing 85 respondents spread across Indonesia. The results of this study show that the risk appetite of Indonesian Muslim investors is risk-averse, and they consider sharia aspects in their investment decision. Nonetheless, the compliance to sharia varies among them. Hence, Indonesian Muslim investors cannot be seen and be treated as a homogenous group.