This volume contains the proceedings of the Combined 19th International Workshop on Expressiveness in Concurrency and the 9th Workshop on Structural Operational Semantics (EXPRESS/SOS 2012) which was held on September 3, 2012 in Newcastle upon Tyne, United Kingdom, as an affiliated workshop of CONCUR 2012, the 23th International Conference on Concurrency Theory. The EXPRESS workshops aim at bringing together researchers interested in the expressiveness of various formal systems and semantic notions, particularly in the field of concurrency. Their focus has traditionally been on the comparison between programming concepts (such as concurrent, functional, imperative, logic and object-oriented programming) and between mathematical models of computation (such as process algebras, Petri nets, event structures, modal logics, and rewrite systems) on the basis of their relative expressive power. The EXPRESS workshop series has run successfully since 1994 and over the years this focus has become broadly construed. The SOS workshops aim at being a forum for researchers, students and practitioners interested in new developments, and directions for future investigation, in the field of structural operational semantics. One of the specific goals of the SOS workshop series is to establish synergies between the concurrency and programming language communities working on the theory and practice of SOS. Reports on applications of SOS to other fields are also most welcome, including: modelling and analysis of biological systems, security of computer systems programming, modelling and analysis of embedded systems, specification of middle-ware and coordination languages, programming language semantics and implementation, static analysis software and hardware verification, and semantics for domain-specific languages and model-based engineering. In 2012, the EXPRESS and SOS communities organized a combined EXPRESS/SOS 2012 workshop on the formal semantics of systems and programming concepts, and on the expressiveness of mathematical models of computation. We received seventeen submissions out of which the programme committee selected ten for presentation at the workshop. These proceedings contain these selected contributions. The workshop also had an invited presentation: Applying automata and games to simply typed lambda calculus, by Colin Stirling (University of Edinburgh, United Kingdom). We would like to thank the authors of the submitted papers, the invited speaker, the members of the programme committee, and their subreviewers for their contribution to both the meeting and this volume. We also thank the CONCUR 2012 organizing committee for hosting EXPRESS/SOS 2012. Finally, we would like to thank our EPTCS editor Rob van Glabbeek for publishing these proceedings and his help during the preparation.