Family caregivers play an important role in the rehabilitation of stroke survivors. The aims of this study were to describe preparedness, uncertainty, and knowledge regarding stroke in family caregivers of people who have undergone strokes and to investigate factors influencing preparedness. A total of 306 caregivers completed the questionnaires, including the Caregiver Preparedness Scale, the Mishel Uncertainty in Illness Scale, and Knowledge of Stroke. The result showed that the mean score of the family caregivers' preparedness was 14.42, the mean score of disease uncertainty was 75.62, and the mean score of stroke knowledge was 10.41. Caregiver preparedness was negatively correlated with disease uncertainty and positively correlated with knowledge. Multivariate stepwise regression analysis showed that educational background, profession, caregiving experience and uncertainty degree of the family caregivers, gender, and age of stroke survivor could predict 45.90% of the total variation in preparedness. The findings suggest that demographic characteristics of stroke survivor and family caregiver, as well as caregivers' disease uncertainty, enable predict the level of caregiver preparedness. Medical professionals should pay attention to providing personalized and targeted approaches to maximize caregivers' preparedness.