In the study of fabric behavior, it is usually assumed that the fabric is uniform. However, in practice, there are some sources of local irregularities in fabric, such as mass irregularity of the yarns. Thus, the mechanical properties will be non-uniform and will differ from place to place. The main aim of this work is to consider and investigate the effect of local irregularities on the tensile behavior of a fabric using a macro scale modeling approach. Initially, tensile samples of nylon 66/polyester fabrics are degraded using a UV light source. Different exposure times are used to induce controlled degradation. The samples are then dyed. The differences in color parameters of the samples are related to their tensile behavior using a Neural Network approach. The tensile parameters of the fabric with each shade of color are measured using a tensile testing machine. In parallel, the macro modeling of the irregular fabric behavior under uni-axial extension is developed using the finite element method and a user material subroutine (UMAT) within the Abaqus environment for applying the material parameters. Then, two fabric samples for the bias extension test are produced. One of them is exposed to a pattern of UV light to obtain an irregular shade of color of the fabric surface. The second is used unexposed. The two samples are tested in the bias extension test in the tensile testing machine and the experimental results are compared to the numerical results and discussed. Shear strain calculated by FEM and measured at different points on the samples are in good agreement both for the virgin material and for the irregular degraded sample. Keywords : plain-woven fabrics, tensile behavior, UV degradation, Finite element method, local irregularities