Advanced multimorbidity is the term used to describe when someone has multiple chronic conditions including those which are associated with palliative care needs. People living with advanced multimorbidity have to coordinate and undertake lots of different tasks related to their chronic conditions, and this can lead to them feeling overburdened, and disengagement from treatment regimes. In this study, we sought to explore how this "treatment burden" was experienced by people with advanced multimorbidity and their caregivers. We adopted a focussed ethnographic approach, in which patient/carer dyads (six groups of two, recruited from an emergency department) took part in two semi-structured interviews and kept a participant-led journal of treatment burden experiences. We also offered to observe any burdensome activities, although only one such session was conducted. A reflexive thematic analysis of the data was conducted by a single researcher, in which data were coded both inductively and through the lens of Burden of Treatment Theory, plus two theories of uncertainty (Total Uncertainty and Uncertainty Tolerance). The types of patient work were split between practical tasks (such as taking medicines or going to hospital) and cognitively burdensome activities (such as symptom surveillance and planning ahead). Burden of Treatment Theory was useful in understanding how work was distributed between patients and their relational networks. We found that multidimensional uncertainty mediated the balance between workload and capacity, and we propose a conceptual model of this relationship alongside a suggestion for how interventions can be used to manage uncertainty and burden.