The International Workshop on Understanding Public Perceptions for Applied Data Science(UPP4DS'21) presents interdisciplinary contributions that address AI trustworthiness from the perspective of the public as end-users. With healthcare as the context for discussion, the workshop will bring together leading experts in applied data science, healthcare, public policy, and social sciences to examine the role of public trust and public engagement in the development of healthcare AI applications. The workshop will also feature original research from the social sciences with significant implications in the adoption of healthcare technologies and invite open discussions on the role of society in the development of acceptable technologies.