Islam encourages the human beings to have a spirit of entrepreneurship. For that reason, investment is considered important concern in business. However, making decision on investment by the Moslems still needs great attention. The study aimed to investigate the determinants of Moslem entrepreneurs when they are trying to make a decision in investment. It utilized descriptive design. Some variables proposed as determinants are Islamic transaction principle, overconfidence, and risk perception. The analysis was done by using survey method on Sidoarjo’s Moslem entrepreneurs and GeSCA software. Based on such analysis, it was found that Islamic transaction principles are somewhat not really implemented comprehensively by Moslem entrepreneurs. They made decisions based on ratio of the probability of success or failure, to what extent it can increase success and reduce failure. The ability to take risks depends on the self-confidence and ability to seek opportunities. Hence, entrepreneurs should accept the risks associated with business failure.