This paper examines the effects of capital structure decisions on the financial risk of a BOT concessionaire. Capital structure decisions affect the costs of capital of both equity and debt holders and therefore are relevant to a project's success. This paper employs the case of Taipei medium-price BOT Hotel Project to conduct the investigation. The results show that different capital structures significantly affect the performance of the project under different scenarios either in terms of net present value or modified internal rate of return. The results show that capital structure decisions are crucial to BOT project success. Hence, all related interested parties, governments, banks, and investors should pay special attention to it.