Background: Patients with incurable cancer face complex medical decisions. Their family caregivers play a prominent role in shared decision making processes, but we lack insights into their experiences. In this study, we explored how bereaved family caregivers experienced the shared decision making process. Methods: We performed a qualitative interview study with in-depth interviews analysed with inductive content analysis. We used a purposive sample of bereaved family caregivers (n = 16) of patients with cancer treated in a tertiary university hospital in the Netherlands. Results: Four themes were identified: 1. scenarios of decision making, 2. future death of the patient 3. factors influencing choices when making a treatment decision, and 4. preconditions for the decision making process. Most family caregivers deferred decisions to the patient or physician. Talking about the patient's future death was not preferred by all family caregivers. All family caregivers reported life prolongation as a significant motivator for treatment, while the quality of life was rarely mentioned. A respectful relationship, close involvement, and open communication with healthcare professionals in the palliative setting were valued by many interviewees. Family caregivers' experiences and needs seemed to be overlooked during medical encounters. Conclusions: Family caregivers of deceased patients with cancer mentioned life prolongation, and not quality of life, as the most important treatment aim. They highly valued interactions with the medical oncologist and being involved in the conversations. We advise medical oncologists to take more effort to involve the family caregiver, and more explicitly address quality of life in the consultations.