This book constitutes the refereed post-conference proceedings of the 16th International Conference on Persuasive Technology, PERSUASIVE 2021, held as a virtual event, in April 2021.The 17 full papers presented in this book together with 8 short papers were carefully reviewed and selected from 67 submissions. The papers are grouped in topical sections as follows: persuasive affective technology; digital marketing, ecommerce, etourism and smart ecosystems; and persuasion and education.