This book constitutes the proceedings of the 7th International Workshop on Graphical Models for Security, GramSec 2020, which took place on June 22, 2020. The workshop was planned to take place in Boston, MA, USA but changed to a virtual format due to the COVID-19 pandemic. The 7 full and 3 short papers presented in this volume were carefully reviewed and selected from 14 submissions. The papers were organized in topical sections named: attack trees; attacks and risks modelling and visualization; and models for reasoning about security.