Background: Due to the increasing care needs of older adults, family caregivers are more and more solicited. This can have a negative impact on their quality of life related to a lack of preparedness for caregiving and feelings of burden. Objectives: To measure perceptions of burden and preparedness for caregiving among the family caregivers of hospitalised older adults, and to explore their possible associations. Methods: A cross-sectional study conducted in two university hospital geriatrics wards in Switzerland. Principal family caregivers of hospitalised older adults were invited to complete sociodemographic, the Zarit Burden Interview, and the Preparedness for Caregiving Scale questionnaires. Descriptive and correlational data analyses were performed. Results: Of the 38 responding caregivers, 80% provided informal care to their spouse or parent; 45% reported a lack of preparedness to provide care and 61% reported substantial levels of burden. There was no statistically significant correlation between preparedness and burden (ρ ≤ −0.30, p = 0.07). Conclusions: A significant proportion of caregivers reported burden and a lack of preparedness. Healthcare professionals should provide adequate support to help informal caregivers to fulfil their roles.