Comprehension and satisfaction are relevant criteria for evaluating the effectiveness of information provided to family members of intensive care unit (ICU) patients. We performed a prospective randomized trial in 34 French ICUs to compare comprehension of diagnosis, prognosis, treatment, and satisfaction with information provided by ICU caregivers, in ICU patient family representatives who did (n = 87) or did not (n = 88) receive a family information leaflet (FIL) in addition to standard information. An FIL designed specifically for this study was delivered at the first visit of the family representative: it provided general information on the ICU and hospital, the name of the ICU physician caring for the patient, a diagram of a typical ICU room with the names of all the devices, and a glossary of 12 terms commonly used in ICUs. Characteristics of the ICUs, patients, and family representatives were similar in the two groups. The FIL reduced the proportion of family members with poor comprehension from 40.9% to 11.5% (p < 0.0001). In the representatives with good comprehension, the FIL was associated with significantly better satisfaction (21 [18 to 24, quartiles] versus 27 [24 to 29, quartiles], p = 0.01). These results indicate that ICU caregivers should consider using an FIL to improve the effectiveness of the information they impart to families.