Free vibration analysis of size‐dependent carbon nanotube‐reinforced composite (CNTRC) nanoplates, resting on the visco‐Pasternak foundation is studied. The Mori–Tanaka approach, considering carbon nanotube (CNT) agglomeration, is employed to derive the material properties of the composite nanoplates. The analysis is carried out for the uniform distribution (UD) and randomly oriented (RO) distribution of single‐walled carbon nanotubes (SWCNTs) while the nanoplate and the foundation are considered to be temperature‐dependent. Using Hamilton's principle, the governing differential equations are derived based on the Eringen's nonlocal elasticity theory and sinusoidal shear deformation theory (SSDT). The natural frequency of the nanoplates is then obtained by the Navier's analytical solution. To verify the method presented, the results are compared with those in the literature. Detailed parametric studies are performed to discuss the influences of CNTs agglomeration, nonlocal parameter, temperature, foundation parameters, the volume fraction of CNTs, plate length‐to‐thickness, and aspect ratios on the free vibration of the CNTRC nanoplates. POLYM. COMPOS., 40:E1479–E1494, 2019. © 2018 Society of Plastics Engineers