In many societies, people with cognitive disability have been pre- sumed to lack reasoned decision-making capacity. Consequently, substituted decision-making laws and practices have traditionally authorised some people such as parents, guardians or medical professionals, to make decisions on their behalf. Several countries are now moving towards an alternative supported decision-making paradigm whereby people with different cognitive abilities are supported to make decisions that reflect as much as possible their ‘will, preferences and rights’. In this paper we examine how geo- graphical thinking about temporalities might illuminate some of the legal, ethical and practical complexities of supported decision- making. The paper draws on qualitative data from interviews with people with intellectual disabilities or acquired brain injury, and those who support them in making decisions. We examine how temporal scales and boundaries shape the determination of decision-making capacity; how decision-makers’ ‘will and preferences’ are interpreted by supporters; and how the labour of support for decision-making is organised. We argue that further geographical engagement with supported decision-making can help significantly advance this important disability rights agenda.