This paper aimed to investigate the nonclassical size dependent free vibration behavior of regularly squared cutout viscoelastic nanobeams nanobeams. The nonlocal strain gradient elasticity theory is modified and adopted to incorporate the viscoelasticity effecteffect. The Kelvin Voigt viscoelastic model is adopted to model the linear viscoelastic constitutive response response. To explore the influence of shear defo rmation effect due to cutout cutout, both Euler Bernoulli and Timoshenko beams theories are considered considered. The Hamilton principle is utilized to derive the dynamic equations of motion incorporating viscoelasticity and size dependent eff ectsects. Closed form solutions fo r the resonant frequencies for both perforated Euler Bernoulli nanobeams (PEBNB) and perforated Timoshenko nanobeams (PTNB) are derived considering different boundary conditions conditions. The developed procedure is verified by comparing the obtained results with th e available results in the literature literature. Parametric studies are conducted to show the influence of the material damping damping, the perforation perforation, the material and the geometrical parameters as well as the boundary and loading conditions on the dynamic behavior of vi scoelastic perforated nanobeams nanobeams. The proposed procedure and the obtained results are supportive in the analysis and design of perforated viscoelastic NEMS structures structures.