Background Brain tumours are the second most common form of childhood cancer, accounting for over 20% of all cases in European children. Understanding the impact of diagnosis and treatment of a brain tumour on the family is an essential pre‐requisite to identifying ways to provide effective support. Aim (1) To explore the impact of having a child with a brain tumour on the main caregiver in the family; (2) to describe mothers' experiences of coping with their child's illness, including personal barriers and strengths; and (3) to identify causes of stress and sources of support to inform improvements in care delivery. Method Participants were drawn from a group of caregivers enrolled in a longitudinal study of outcome following diagnosis of a childhood brain tumour. Six caregivers took part, two from each of the high‐, medium‐ and low‐impact groups based on their Impact on Families Scale scores. Semi‐structured interviews were used, with questions covering: (1) impact of the diagnosis on main caregiver and family; (2) personal barriers and strengths; and (3) causes of stress and sources of support. Interviews were transcribed verbatim and coded manually into five themes, which comprised 19 subthemes. Findings Coping methods and provision of help and support were major preoccupations for main caregivers from all impact groups. Caregivers in the high‐impact group reported less conflict. High‐ and medium‐impact group caregivers had experienced less ‘hindrance and heartache’, than those with low impact scores, suggesting that the stress associated with diagnosis and treatment of the tumour may have increased cohesion and acceptance within these families. Conclusion Families of children diagnosed with a brain tumour experience considerable negative impact and may perceive themselves as struggling to cope. Provision of help and support, within and outside the extended family, including from health, education and other services, is perceived as helpful.