Aerosol reactors are utilized to manufacture nanoparticles in industrially relevant quantities. The development, understanding, and scale-up of aerosol reactors can be facilitated with models and computer simulations. An overview of recent developments of models and simulations is presented and their interconnection in a multiscale approach is discussed. A short introduction of the various aerosol reactor types and gas-phase particle dynamics is provided as a background for the later discussion of the models and simulations. Models are presented with decreasing time and length scales in sections on continuum, mesoscale, molecular dynamics, and quantum mechanics models.