This volume contains a selection of the papers presented at the 10th Inter- tional Workshop on Multi-Agent-Based Simulation (MABS 2009), a workshop co-located with the 8th International Conference on Autonomous Agents and Multiagent Systems (AAMAS 2009), which was held during May 10-15,2009, in Budapest, Hungary. The MABS Workshops Series continues to representan important event that brings together researchers from the multi-agent systems community and the social simulation one. There were 43 submissions for the 2009 edition, each one reviewed by at least three Programme Committee members,...