Purpose: Caregivers of patients with cancer play an important role throughout the treatment trajectory. This can be challenging and might infer health and psychosocial problems. This may especially be the case in caregivers of patients with cancers that carry a high risk of recurrence such as cancers of the pancreas, duodenum and bile duct. This study therefore explored the experiences of caregivers of patients attending follow-up after completion of treatment with curative intent for cancers of the pancreas, duodenum and bile duct. Methods: A qualitative study using semi-structured, individual interviews. Data were analysed using content analysis. Results: Ten caregivers of patients attending follow-up after completed curative treatment for cancers of the pancreas, duodenum and bile duct in a specialized gastro-surgical center at a tertiary hospital in the Capital Region of Denmark participated. We identified three themes: “From bystander to enlisted carer”, inferring that caregivers felt enlisted as carers during treatment and follow-up, however without sufficient instruction or assessment of their needs. “Lonesome worrying” meaning that caregivers hid their feelings of concern and foreboding, and finally, “Keeping a stiff upper lip” indicating that caregivers outwardly maintained a positive face when interacting with the patient. Conclusion: Caregivers described taking on a substantial burden of care without feeling competent. They experienced distress and emotional isolation which affected their relationship with the patient and their mutual coping. The results indicate a need for health care professionals to facilitate reflection on the needs and roles of both patients and caregivers throughout the treatment trajectory.