Synopsis: Preliminary studies suggest that flexible ICU visiting hours (up to 12 hours per day) have beneficial effects on patient delirium, stress reduction, and family satisfaction, but potentially detrimental effects on patient care via infections, disorganized/disrupted care, and provider burnout. The default policy of most ICUs is to have restricted visiting hours (<4.5 hours per day). In this cluster-crossover randomized trial in Brazil, ICUs were randomized to flexible followed by restrictive visiting policies or vice versa to assess patient, caregiver, and provider outcomes. The primary outcome was incidence of delirium, secondary outcomes included ICU-acquired infections, 7-day ventilator-free days, LOS, hospital mortality, caregiver anxiety, caregiver depression, caregiver satisfaction, clinician burnout, and tertiary outcomes included use of restraints, self-perception of involvement, perceived disorganization of care, and conflicts with visitors. The study recruited 1685 patients, 1060 family members, and 737 clinicians from April 2017 to June 2018. Family had a daily mean visit duration of 4.8 hours vs 1.4 hours in flexible vs restricted policies. There was no significant difference in the incidence of delirium (18.9% in flexible vs 20.1% in restricted) as well as no difference in ICU-acquired infections, ventilator-free days, LOS, mortality, and provider burnout. There was statistically significant improvement in caregiver anxiety, depression, and satisfaction. Therefore, the study concludes that flexible visitation policies did not improve ICU delirium but did improve the experience of family and caregivers without harm to patients or disruption to the ICU care team. Limitations include middle-income country setting that may not be generalizable, short duration of visiting time with patients despite flexible visiting hours, and lack of long-term follow-up on the impact on provider burnout.