This book constitutes the refereed proceedings of the 6th IFIP TC 6 International Workshop on Self-Organizing Systems, IWSOS 2012, held in Delft, The Netherlands, in March 2012. The 5 revised full papers and 5 short papers presented together with 2 invited papers were carefully selected from 25 full paper and 8 short paper submissions. The papers address the following key topics, design and analysis of self-organizing and self-managing systems, inspiring models of self-organization in nature and society, structure, characteristics and dynamics of self-organizing networks, techniques and tools for modeling self-organizing systems, robustness and adaptation in self-organizing systems, self-organization in complex networks like peer-to-peer, sensor, ad-hoc, vehicular and social networks, control of self-organizing systems, decentralized power management in the smart grid, self-organizing group and pattern formation, self-organizing mechanisms for task allocation, coordination and resource allocation, self-organizing information dissemination and content search, and risks and limits of self-organization.