The Symposium on Software Performance: Joint Kieker/Palladio Days 2013, which took place November 27-29 (Wed-Fri), 2013 in Karlsruhe, Germany, brought together researchers and practitioners interested in all facets of software performance, ranging from modeling and prediction to monitoring and management. The symposium was organized by two already established user groups: for the first time, the Kieker and the Palladio communities had a joint meeting in form of this symposium. Kieker is a well-established tool and approach for monitoring software performance of complex, large, and distributed IT systems. Palladio is a likewise-established tool and approach for modeling software architectures of IT systems and for simulating their performance. However, contributions were not limited to these two communities but we also welcomed contributions from the field.