Questions of how to harness digital technologies for promoting mental health are a hotbed of governmental, health policy and social debate. Campaigns for optimizing digital healthcare largely focus on promoting patient responsibilization, encouraging the development of more informed patients who draw on digital resources as part of self-care projects. Arguably, however, while “self-care” often involves the promotion of patient self-responsibility, it simultaneously foregrounds other modes of ethical engagement, such as care for, or from, (known/unknown) others and concerns over states’ and corporations’ responsibilities for ensuring mental wellbeing. Indeed, the broader literature on responsibility suggests that rather than an overriding emphasis on personal responsibility, advanced liberal societies create a much more fertile and contested ground upon which multiple, competing responsibilities flourish, even as part of projects of self-care. Digital technologies add additional layers to how responsibility is enacted, reshaping experiences of time and space by enabling new forms of continuous, or seemingly continuous, person-person and person-technology relations, and consequently refracting users’ sense of where agency lies (i.e. in themselves, in their relations with (human) others, or in technologies themselves). Online activities furthermore often involve multiple temporal horizons, in terms of enactments of care as well as the perceived trajectories of mental health. Drawing on a case study of a newly emerging online ethics engaged in by young New Zealanders, this paper examines how interpersonal dynamics, human-technology relations, and questions of agency are recasting understandings and enactments of care, temporality and responsibility in young people’s efforts to secure mental wellbeing.