This book constitutes the proceedings of the Third Joint International Conference on Serious Games, JCSG 2017, held in Valencia, Spain, in November 2017. This conference bundles the activities of the 8th International Conference on Serious Games Development and Applications, SGDA 2017, and the 7th Conference on Serious Games, GameDays 2017. The total of 23 full papers, 3 short papers, and 4 poster papers was carefully reviewed and selected from 44 submissions. The topics covered by the conference offered participants a valuable platform to discuss and learn about the latest developments, technologies and possibilities in the development and use of serious games with a special focus on how different fields can be combined to achieve the best possible results.