In this research notes book, the modelling of mechanical properties of CNT/polymer nanocomposites is presented. The book begins with the structural and intrinsic mechanical properties of CNTs and then introduces computational methods that have been applied to polymer nanocomposites, covering from molecular scale (molecular dynamics, Monte Carlo), microscale (Brownian dynamics, dissipative particle dynamics, lattice Boltzmann, time-dependent Ginzburg-Landau method, dynamic density functional theory method) to mesoscale and macroscale (micromechanics, equivalent-continuum and self-similar approaches, finite element method).