This book constitutes the refereed proceedings of the Third EAI International Conference on Smart Objects and Technologies for Social Good, GOODTECHS 2017, held in Pisa, Italy, November 29-30, 2017. The 38 revised full papers presented were carefully reviewed and selected from 70 submissions. The papers reflect the design, implementation, deployment, operation and evaluation of smart objects and technologies for social good. A social good can be understood as a service that benefits a large number of people in a most possible way. Some classic examples are healthcare, safety, environment, democracy, and human rights, or even art, entertainment, and communication.