Models of carbon nanotubes (CNTs) in their perfect and imperfect form were simulated and their mechanical behavior was investigated through performing torsion and tensile tests. Afterwards, three kinds of imperfections, i.e., twisting angle, z-distortion along the longitudinal axis, and xy-distortion along the radial axis, were introduced to the configuration of perfect CNTs and the tensile and shear behavior of imperfect CNTs was numerically evaluated and compared with the behavior of the perfect ones. It was indicated that the existence of any type of imperfection in the structure of CNTs leads to a lower tensile and shear resistance of perfect CNTs. However, this trend was more visible for the CNTs with higher chirality.