This article extends the evaluation techniques of an irrigation dam in northern Greece, called “Petrenia”, by comparing the real options approach along with, a traditional one, the discount cash flow. By introducing first a Monte Carlo simulation, the various uncertainty factors can be simulated and alternative value options can be computed, feeding them later in the real options model. Results from the case study in Greece clearly demonstrate that the irrigation dam can be classified as a profitable investment, by applying traditional discount cash flow analysis, while by applying the real options approach the project cannot be classified as profitable. Taking into consideration the uncertainty factors, the real options approach reveals that the investment could be postponed and decision makers can keep the option of investing open. Sequentially, discount cash flow analysis accompanied by the real options approach facilitates decision making and improves the investment assessment analysis. In this particular project assessment, two uncertainty factors, variation in dam capacity and water price, restrict the profitability of the irrigation dam, according to the results of the real options approach.