Nowadays, IIR continues to increase in complexity: user tasks and needs are demanding; data and information systems are rapidly evolving and greatly heterogeneous; and the interaction between users and IR systems is much more articulated. For example, consider what Web search is today: highly diversified results are returned from Web pages, news, social media, image and video search, products and more, and all are merged through adaptive strategies driven by current and previous user-systems interactions. As a result, experimental evaluation needs to appropriately model these evolving tasks, needs, data sources and user interactions. An additional challenge pertains to the anticipated outcome of IIR research and application. It is no longer sufficient to focus solely on precision, recall and satisfaction: successful IIR systems must engage, inform, and relate to users, taking into account single session and more long-term use and re-use. To progress current evaluation methodologies and ensure they are able to effectively support the development of next generation IIR systems, one of the most compelling prospects is to bridge system-oriented and user-oriented evaluation methods. Both methodological approaches have their advantages and drawbacks: while system-centered methods ensure greater internal validity, they may fail to take into account user and contextual factors that influence IIR; user-oriented methods may better approximate actual user behavior, affect and cognition, but provide less experimental control of independent variables. The goal of this workshop is to unite system- and user-centered IIR researchers for the purposes of: Sharing different user-centered and system-centred research methods, measures, and tools in order to foster knowledge exchange; Exploring the addition of user-centered evaluation strategies to system-oriented studies, and vice versa; and Initiating collaborations between user- and system-oriented researchers to further IIR research.