In the framework of nonlocal strain gradient theory, a size-dependent symmetric and sigmoid functionally graded (FG) Timoshenko beam model is developed to study and analyze the free vibration and dynamic response under moving load, for the first time. To incorporate the size-dependent effect, the nonlocal strain gradient theory is adopted. The Hamilton principle is employed to drive the dynamic equations of motion and the associated boundary conditions. Based on Navier’s approach, an analytical solution methodology for free and forced vibration problems is developed. The developed methodology is verified by comparing the obtained results with the available resources and good agreement is observed. Numerical results are obtained and discussed. Effects of the material gradation index, nonlocal parameter, microstructure length scale parameter, and the nondimensional velocity parameter of the moving load on the dynamic behavior are investigated. It is found that these variables significantly affect the dynamic behavior of the functionally graded nanobeams, and they could be adjusted to control this behavior. Obtained results are supportive of the design and control of such types of structural components.