This volume constitutes the refereed proceedings of the 6th European Performance Engineering Workshop, EPEW 2009, held in London, UK during July 9-10, 2009. The 13 full papers and 4 short papers presented in this volume, together with the abstract of one invited paper, were carefully reviewed and selected from 33 submissions. The papers deal with modeling of auctions and markets, hardware modeling of RAID systems, performance aspects of cellular and fixed-line networks, mean value analysis, stochastic ordering to queuing networks, extension of passage-time analysis, stochastic process algebra (PEPA), tagged customers in generalised stochastic Petri nets, and representation and analysis of generally-distributed stochastic systems.