Brain tumor patients confront numerous challenges arising from diagnosis and treatment, and these impact the patient's physical, mental, and social functions at all levels. Primary informal caregivers assume a pivotal role in home-based patient care. Of particular importance are the coping strategies employed by family caregivers, as they can influence both their own health and the overall quality of home care. This study aimed to explore the associations among family function, caregiving competence, and coping strategies among primary informal caregivers. This study adopted a cross-sectional correlational design and convenience sampling to survey the primary informal caregivers of 111 brain tumor patients. The study instruments included the Family Assessment Device General Function, Caregiving Competence Scale, and Revised Ways of Coping Checklist. The findings of this study revealed a significant positive correlation between the family function of primary informal caregivers and their employment of emotion-focused coping (r = 0.209, p < 0.05). Furthermore, caregiving competence exhibited a positive association with problem-focused coping (r = 0.242, p < 0.05) and emerged as a significant predictor of problem-focused coping (β = 0.182, p < 0.05). However, neither family function (r = 0.059, p < 0.05) nor caregiving competence (r = 0.031, p < 0.05) demonstrated significant associations with total coping strategies. The findings of this study affirmed that enhancing the caregiving competence of primary informal caregivers of brain tumor patients can facilitate the adoption of problem-focused coping strategies.