Graphs are used as models in many areas of computer science and computer engineering. For example graphs are used to represent syntax, control and data flow, dependency, state spaces, models such as UML and other types of domain-specific models, and social network graphs. In all of these examples, the graph serves as an intuitive yet mathematically precise foundation for many purposes, both in theory building as well as in practical applications. Graph-based models serve as an abstract communication medium and are used to describe various concepts and phenomena. Moreover, once such graph-based models are constructed, they can be analyzed and transformed to verify the correctness of static and dynamic properties, to discover new properties, to deeply study a particular domain of interest or to produce new equivalent and/or optimized versions of graph-based models. The Graphs as Models (GaM) workshop series combines the strengths of two pre-existing workshop series: GT-VMT (Graph Transformation and Visual Modelling Techniques) and GRAPHITE (Graph Inspection and Traversal Engineering), but also solicits research from other related areas, such as social network analysis. GaM offers a platform for exchanging new ideas and results for active researchers in these areas, with a particular aim of boosting inter- and transdisciplinary research exploiting new applications of graphs as models in any area of computational science. This year (2017), the third edition of the GaM workshop was co-located with the European Joint Conferences on Theory and Practice of Software 2017 (ETAPS'17), held in Uppsala, Sweden.