The provision of informal care presents a significant global challenge. To better understand how cultural factors underpin and shape motivations and willingness to provide informal care for adults, an in-depth qualitative synthesis was conducted. Six electronic databases and a wide range of additional sources were searched. Following meta-ethnographic guidelines, 37 qualitative studies were synthesised. Six main concepts were identified: cultural self-identity, which appeared as an overarching explanatory concept; cultural duty and obligations; cultural values; love and emotional attachments; repayment and reciprocity; and competing demands and roles. These concepts informed a model of cultural caregiving motivations, offering an inductive-based exploration of key cultural motivators and highlighting implications for theory development, future research, policy and practice. The model holds implications for the actual exchange of care. Caregiver motivations should not be taken for granted by healthcare or social care professionals involved in assessment and support planning, educational endeavours at a population level may support caregiving, and support should be sensitive to cultural caregiving motivations.