Objectives: Motor neurone disease (MND) is a progressive, life-limiting illness. Caregiving impacts greatly on family carers with few supportive interventions for carers. We report Stages 1 and 2 of a study to: (1) explore experiences of MND caregiving and use carer-identified support needs to determine suitability and acceptability of the Carer Support Needs Assessment Tool (CSNAT), (2) adapt the CSNAT as necessary for comprehensive assessment and support of MND carers, prior to (Stage 3) feasibility testing. Design: Qualitative: focus groups, interviews and carer workshops. Setting: Three UK MND specialist centres serving a wide range of areas. Participants: Stage 1: 33 carers, 11 from each site: 19 current carers, 14 bereaved. Stage 2: 19 carer advisors: 10 bereaved, 9 current carers. Majority were spouses/partners ranging in age from under 45 years to over 75 years. Duration of caring: 4 months to 12.5 years. Results: Carers described challenges of a disease that was terminal from the outset, of ‘chasing’ progressive deterioration, trying to balance normality and patient independence against growing dependence, and intensive involvement in caregiving. Carers had extensive support needs which could be mapped to existing CSNAT domains: both ‘enabling’ domains which identify carers’ needs as co-workers as well as carers’ ‘direct’ needs as clients in relation to their own health and well-being. Only one aspect of their caregiving experience went beyond existing domains: a new domain on support needs with relationship changes was identified to tailor the CSNAT better to MND carers. Conclusions: Carers of people with MND found the adapted CSNAT to be an appropriate and relevant tool for assessment of their support needs. The revised version has potential for assessment of carers in other longer-term caring contexts. A further paper will report the Stage 3 study on feasibility of using the adapted CSNAT in routine practice.