BACKGROUND Low-dose tacrolimus-based immunosuppression is a standard therapy in kidney and liver transplantation; however, the optimal therapeutic level of tacrolimus has not been established in lung transplantation. We aimed to identify the tacrolimus level associated with better outcomes in lung transplant patients. METHODS This retrospective study included patients who underwent lung transplantation at Seoul National University Hospital between 2006 and 2016. Kaplan-Meier survival analysis and Cox regression were performed according to tacrolimus levels at several time-points within 1-year posttransplantation. RESULTS A total of 43 patients received bilateral lung transplantation. The median age was 53 years and the median follow-up was 20.5 months. Overall and 1-year patient survival rates were 55.8% and 74.4%, respectively. Infection was the most common cause of death (78.9%). Chronic lung allograft dysfunction was observed in 16.3%. A tacrolimus level <9 ng/ml at 1 month was associated with lower rejection-free survival (P = 0.009). A time-averaged tacrolimus level <10 ng/ml within 1 month posttransplantation was an independent risk factor for poor patient survival (hazard ratio: 4.904; 95% confidence interval: 1.930-12.459; P= 0.001). Furthermore, higher tacrolimus levels did not increase infectious complications. CONCLUSIONS These finding suggest that tacrolimus levels ≥10 ng/ml within 1 month after lung transplantation appear to be associated with better patient survival.