The stable immunosuppressant level at the early period after kidney transplantation (KT) is one of the most important factors for the prognosis of KT. However, the extent of immunosuppression varies according to the policies of each KT center. We investigated the relationship between the clinical outcome and tacrolimus trough level (TTL) at the early post-transplant period.We retrospectively analyzed medical records of patients who underwent KT between July 2007 and June 2016. We investigated TTLs at 3 months after KT. We evaluated the incidence of biopsy-proven acute rejection (BPAR), cytomegalovirus infection, and graft survival according to the TTLs.A total of 426 patients who received KT during the study period were enrolled. The mean age of KT recipients was 46.3 ± 11.5 years, and 55.5% of patients were men. The incidence of BPAR within 1 year after KT was significantly higher when TTLs at 3 months were less than 4.0 ng/mL (P = .020). Death-censored graft survival rates were significantly lower in KT recipients with BPAR and TTL less than 4.0 ng/mL (P < .001, P < .001, respectively). In multivariate analysis, BPAR and TTL less than 4.0 ng/mL at 3 months after KT were independent risk factors for graft failure.BPAR and TTL less than 4.0 ng/mL at 3 months after KT are important risk factors for allograft failure. Therefore, TTL should be kept at least 4.0 ng/mL or more at 3 months after KT to reduce the incidence of BPAR within 1 year after KT.