This study uses a genetic algorithm and Monte Carlo Simulation to value American put options by trying to make optimal early exercise decisions. In the literature, some researchers have proposed approaches to valuing American options by using Monte Carlo simulation. Most of the approaches rely on the estimation of the value of continuing at each early exercise point. Once the estimated value of continuing has been obtained, early exercise decision can be made by comparing this value with the value of exercising. In this study, American put options will be valued without the estimation of the value of continuing. A genetic algorithm will be used to assist the Monte Carlo method in making the early exercise decisions as optimally as possible. This is possible because better early exercise decisions can bring about a bigger expected discounted profit.