This volume contains the proceedings of the 17th International Workshop on Expressiveness in Concurrency (EXPRESS'10), which took place on 30th August 2010 in Paris, co-located with CONCUR'10. The EXPRESS workshop series aim at bringing together researchers who are interested in the expressiveness and comparison of formal models that broadly relate to concurrency. In particular, this also includes emergent fields such as logic and interaction, game-theoretic models, and service-oriented computing.