Objective To explore the care adaptation experiences of family caregivers of patients with neurological critical illness, providing reference for promoting family support. Methods A phenomenological research method was used to conduct semi-structured in-depth interviews with 17 family caregivers of patients hospitalized for neurological critical illness. Colaizzi′s seven-step method was applied to analyze the interview data. Results Four themes and twelve sub-themes were identified, including threats and challenges to adaptation (severe physical burden, heavy mental stress, sudden lifestyle changes, inadequate support systems), positive adaptation experiences (personal growth, mutual growth), coping strategies for adaptation difficulties (self-avoidance and adjustment, seeking support and help), and adaptation needs (enhanced transitional care, desire for professional support, need for respect and encouragement, longing for psychological support). Conclusion The care adaptation experiences of family caregivers of patients with neurological critical illness are complex. Healthcare professionals should provide support and assistance to family caregivers to help them cope with anticipated caregiving difficulties.