BACKGROUND: Family caregivers play an important role in the care of patients receiving palliative care, yet little is known about the financial impact of family caregiving in this context. A lack of existing validated tools for collecting data on the costs of family caregiving in palliative care has resulted in a weak and limited evidence base. The aim of the study was to describe the development and initial piloting of a new survey tool which captures data on the costs of family caregiving in palliative care: the Costs of Family Caregiving (COFAC) questionnaire.