PURPOSE: Long-term mental outcomes in family members of coronavirus disease 2019 (COVID-19) intensive care unit (ICU) survivors are unknown. Therefore, we assessed the prevalence of mental health symptoms, including associated risk factors, and quality of life (QoL) in family members of COVID-19 ICU survivors 3 and 12 months post-ICU. METHODS: A prospective multicentre cohort study in ICUs of ten Dutch hospitals, including adult family members of COVID-19 ICU survivors admitted between March 1, and July 1, 2020. Symptom prevalence rates of anxiety, depression (Hospital Anxiety and Depression Scale) and Post-Traumatic Stress Disorder (Impact of Event Scale-6), and QoL (Short Form-12) before ICU admission (baseline), and after 3 and 12 months were measured. Additionally, associations between family and patient characteristics and mental health symptoms were calculated. RESULTS: A total of 166 out of 197 (84.3%) included family members completed the 12-month follow-up of whom 46.1% and 38.3% had mental health symptoms 3 and 12 months post-ICU, respectively; both higher compared to baseline (22.4%) (p < 0.001). The mental component summary score of the SF-12 was lower at 12-month follow-up compared with baseline [mean difference mental component score: - 5.5 (95% confidence interval (CI) - 7.4 to - 3.6)]. Furthermore, 27.9% experienced work-related problems. Symptoms of anxiety (odds ratio (OR) 9.23; 95% CI 2.296-37.24; p = 0.002) and depression (OR 5.96; 95% CI 1.29-27.42; p = 0.02) prior to ICU admission were identified as risk factors for mental health symptoms after 12 months. CONCLUSION: A considerable proportion of family members of COVID-19 survivors reported mental health symptoms 3 and 12 months after ICU admission, disrupting QoL and creating work-related problems.