For most companies, it is a reality to face uncertainties when conducting complex projects focused on the implementation of Information Systems (IS) and, as a consequence, cost-benefit evaluation of this kind of projects has become a difficult task. In this context, Real Options Theory (ROT) has proved to be a viable alternative to provide methods to evaluate complex projects, not only in Information Technology but in many other economics and business areas. This paper intends to demonstrate how ROT can be applied to evaluate complex Information Technology projects, exploring a case study involving an implementation project of an Enterprise Resource Planning (ERP). In the case study, two distinct solutions for the implementation of an ERP were evaluated, demonstrating the applicability of ROT to such complex situations.