Delirium is one of the common manifestations of acute brain dysfunction in critically ill patients. We aimed to evaluate the effect of family intervention on reducing the delirium incidence in patients hospitalized in the intensive care unit (ICU). We searched electronic databases for randomized clinical trials, cohort, and before-and-after studies up to September 2021 using the MeSH terms ("family" OR "family caregiver") AND ("delirium"). A total of 6 studies including 4199 patients were analyzed. Compared to the control group, the risk of delirium was 24% lower in the family intervention group (OR 0·76 [0·67-0·86], P = 0.20, I2 = 31%). Pooled data from two trials showed that family intervention was associated with fewer delirium days (SMD: -1.13, 95% CI: -1.91 to -0.34; P = 0.08; I2 = 67%;). However, there were no significant differences between the two groups in the length of ICU stay, mechanical ventilation duration, and mortality (ICU stay days: MD: -0.62 days; 95% CI: -1.49 to 0.24; P = 0.14; I2 = 72%; mechanical ventilation days: MD: -0.48 days; 95% CI: -2.10 to 1.13; P = 0.56; I2 = 0%; mortality: OR: 0.68, 95% CI: 0.22 to 2.09; P = 0.08; I2 = 67%). Current evidence supports the use of family intervention in reducing the delirium risk and delirium days in hospitalized ICU patients. However, its effects on reducing ICU stay length, ventilation duration, and mortality require further study. Future research should consider identifying the specific family intervention strategies and their duration.