This book constitutes the refereed proceedings of the 5th InternationalWorkshop on Self-Organizing Systems, IWSOS 2011, held in Karlsruhe,Germany, in February 2011.The 9 revised full papers presented together with 1 invited paper werecarefully selected from 25 initial submissions. It was the 5th workshopin a series of multidisciplinary events dedicated to self-organizationin networked systems with main focus on communication and computernetworks. The papers address theoretical aspects of self-organization aswell as applications in communication and computer networks and robotnetworks.