This book constitutes the thoroughly refereed post-conference proceedings of the 7th International Conference on Modelling and Simulation for Autonomous Systems, MESAS 2020, held in Prague, Czech Republic, in October 2020.*The 19 full papers included in the volume were carefully reviewed and selected from 26 submissions. They are organized in the following topical sections: future challenges of advanced M&S technology; M&S of intelligent systems – R&D and application; and AxS/AI in context of future warfare and security environment. *The conference was held virtually.