This book constitutes the thoroughly refereed post-proceedings of the 13th Agent-Oriented Software Engineering (AOSE) workshop, held at the 11th International Conference on Autonomous Agents and Multiagent Systems, AAMAS 2012, in Valencia, Spain, in June 2012. This volume presents 9 thoroughly revised papers selected from 24 submissions as well as two invited articles by leading researchers in the field. The papers cover a broad range of topics related to software engineering of agent-based systems, with particular attention to the integration of concepts and techniques from multi-agent systems with recent programming languages, platforms, and established software engineering methodologies.