In this study, the effects of uncertain material properties on the buckling response of laminated composite structures based on the isogeometric analysis will be presented. The target modulus of elasticity fields are assumed to be a stochastic field and case studies are considered for laminated composite structures including beams and plates. The spectral representation is employed as the crucial method of generating samples. Numerical results show a successful establishment of spectral representation method based on Monte Carlo simulation and isogeometric analysis for evaluating accurately the effects of uncertain material property on the buckling responses. It is demonstrated that linear-like relations between the standard deviation of modulus of elasticity and the standard deviation of critical buckling load of composite beams and plates are accomplished. In addition, isogeometric analysis, which is employed as a solver for the analysis of composite plate based on C1 four-unknown refined plate theory, remarkably outweighs the finite element analysis approach in terms of computational cost of the simulations.