AbstractDementia often leads to reduced autonomy and the need for help with activities of daily living, such as the use of the lavatory. In response, we present ToiletHelp, a novel system to provide automated, step-by-step guidance to individuals with dementia when using the lavatory. In such an intimate environment, it is crucial to maintain the user’s privacy, which ToiletHelp achieves by sensing only depth maps. ToiletHelp uses a depth sensor to detect when the user is in need of assistance and tailors the guidance accordingly, using a combination of verbal and visual prompts. Our main contribution is the development of the first assistance system for people with dementia in such a sensitive environment as the lavatory. In addition, what sets ToiletHelp apart is its comprehensive involvement of 60 participants, 33 end-users and 27 healthcare workers, throughout its development process. A user-centered evaluation validates the interaction design, demonstrating enhanced feelings of security and independence among older adults, as well as successful comprehension of instructions by participants with dementia. Caregivers report high satisfaction with the system’s modalities and confirm its effectiveness in reducing their workload while assisting end-users. These findings not only validate the success of ToiletHelp and underscore its potential benefits but also contribute to the field of human-computer interaction design. Our comprehensive analysis of the results provides valuable information for researchers developing solutions for individuals with dementia, which is especially valuable given the limited existing literature on the subject.