Objective: Families of patients in the intensive care unit (ICU) often experience severe stress, and understanding their experience is important for maintaining family functioning. This study aimed to determine the characteristics and factors associated with family functioning in families of patients admitted to the ICU. Methods: This cross-sectional study recruited all family members (N = 144) of patients admitted to the ICU at two teaching and advanced treatment hospitals, 77 (53.5%) of whom completed a questionnaire. Family members provided the demographic and clinical characteristics of the patients and completed the Family Relation Index (FRI), the Impact of Event Scale-Revised, the Center for Epidemiologic Studies Depression Scale, the State-Trait Anxiety Inventory (STAI) Form X, the Connor-Davidson Resilience Scale (CD-RISC), and the Social Support Questionnaire. Results: Ten (13.0%) and 37 (48.1%) family members had the "hostile" and "sullen" family functioning type, respectively. Multiple regression analysis revealed the presence of a significant negative relationship between the FRI and the STAI-state (B = −0.057, β = −0.36; p =.001) that the participants had experienced a stressful event within the previous month (B = −1.201, β = −0.276, p =.009), and that the participants' CD-RISC scores were correlated with family functioning (B = 0.021, β = 0.176, p =.049). Moreover, this model explained 23.9% of the variance in total FRI scores with regard to family functioning. Conclusions: In total, 61% of the family members had poor family functioning and required support. Among the family members of patients in the ICU, anxiety was associated with poor family functioning, whereas resilience was associated with good family functioning.