ABSTRACT Masonry is the oldest building material that is still widely used in the building industry. There is a remarkably increasing need nowadays for masonry construction, both financially and socially. However, the analysis of the mechanical behavior of masonry constructions is a true challenge, due to non-homogeneous nature, anisotropy, low tensile strength and other factors. Also, the masonry element exhibits obvious nonlinear behavior. This research focuses on the nonlinear analysis of unreinforced masonry structures. The primary aim is the development and validation of accurate numerical representation of masonry structures considering its nonlinear behavior, which can be easily used by the practicing engineer. The nonlinear analysis is performed using a commercially-available computer program, which renders the approach easily and efficiently applicable by a practicing engineer. Also an experimental program was conducted as part of this research in order to evaluate the ability of the mathematical model proposed to reproduce masonry mechanics by comparing the obtained numerical to experimental results. Validation of the model was also ensured by means of comparison between the calculated numerical results and experimental results available in the literature.