The rise of online experiences in the domain of cultural heritage offers new forms of interaction that are no longer limited by the physical presence of museums. However, sustaining online visitors’ engagement is challenging, and museum professionals seek to understand how to increase motivation. We conducted a user study (N = 32) of three museum websites to investigate users’ intrinsic motivations to engage with the sites through observation, questionnaires, and semi-structured interviews. Building on self- determination theory, we identified design characteristics that meet users’ psychological needs, such as autonomy, competence, and relatedness, and increase their intrinsic motivation to interact with the interface. Our results show that this could consequently lead to higher user engagement. We contribute new empirical insights into the intrinsic motivation mechanisms of museum website visitors, which have relevant implications for the design of museum websites to improve user engagement.