This book constitutes the proceedings of the Third International Symposium on Dependable Software Engineering: Theories, Tools, and Applications, SETTA 2018, held in Beijing, China, in September 2018. The 9 full papers presented together with 3 short papers  were carefully reviewed and selected from 22 submissions. The purpose of SETTA is to provide an international forum for researchers and practitioners to share cutting-edge advancements and strengthen collaborations in the  field of formal methods and its interoperability with software engineering for building reliable, safe, secure, and smart systems.