Objective: To identify the key components of a biopsychosocial support intervention to improve mental wellbeing for informal stroke carers within the first year post-stroke based on the combined perspectives of experts in the field of psychological care after stroke and informal stroke carers themselves. Methods: After reviewing the existing literature a cross-sectional mixed-methods design was adopted comprising 1) focus groups with informal stroke carers about their psychological support needs, and 2) nominal group technique with academic and clinical stroke care experts to reach consensus on intervention priorities. Transcripts were thematically analyzed and combined with the ranked priorities from the nominal group to identify key components for intervention content. Results: Key themes for informal stroke carers were associated with: 1) changes in relationships, roles, and dynamics; 2) emotional impact and acceptance; 3) drawing on inner resources; 4) looking for information, solutions, and explanations; 5) support from others. The expert nominal group placed priority on eight ranked areas: 1) acknowledging "normal" emotions; 2) education about the effects of a stroke; 3) reactions to loss and adjustment; 4) recognizing signs and symptoms of not coping; 5) knowing how and when to access practical and emotional support; 6) strategies for taking care of own health; 7) dealing with difficult emotions; and 8) problem solving skills. Conclusions: Themes from the informal carer focus groups, and ranked priority areas will inform the development of a biopsychosocial support intervention for stroke carers to be tested in a feasibility randomized controlled trial.