Trust in technology is an important factor for the design and use of technology in general. While there is growing interest in the role of trust on this general level, so far little attention has been given to the particularities of trust in persuasive technologies, i.e. technologies that serve to persuade users into certain behaviours. Those technologies are increasingly targeting the older adults, posing ethical questions that ask for sensitive investigation of trust. Here, we explore the specific character of trust in persuasive gerontechnology. We argue that the question of how to establish trust in technology, how to make trust lasting and enduring, requires considering user-centric and institution-centric approaches, and suggest an approach that is sensitive to wider social and institutional factors. The impact that persuasive gerontechnology can have depends on whether people can trust them, the designers, or the overall system. Drawing on studies of determinants of institutional trust, we identify four main strategies that can inform designers, technology assessors and policy makers in building trust between technology and users: (1) creating novel institutions, (2) creating incentives, (3) providing guarantees, and (4) ensuring transparency. We conclude the discussion with suggestions regarding future directions in researching trust and persuasive technology.