Objectives: In liver cirrhosis patients, acute kidney injury (AKI) is considered as an independent prognostic factor for mortality and non-treated AKI can be progressed into hepatorenal syndrome (HRS) with poor prognosis. The suppression of Tumorigenicity 2 protein (ST2) is included in members of IL-1 receptors that aggravates inflammation and fibrotic change in multiple organs. The elevated ST2 level is associated with disease activity and deteriorated kidney function in chronic kidney disease. In this study we analyzed the association between kidney & liver function and ST2 level among liver transplanted (LT) recipients. Methods: We measured soluble ST2 (sST2) levels using ELISA in serum and urine samples that derived from LT recipients. To evaluate the liver function, we checked Model for End-Stage Liver Disease (MELD) scores of LT recipients on the day of LT surgery. Acute kidney injury (AKI) was classified into stage 1, 2, and 3 with changes of creatinine level and history of renal replacement therapy. Results: Significantly increased serum sST2 levels were observed in LT recipients with suppressed kidney function compared with recipients with normal kidney function. However, urine ST2 levels showed no differences between normal and deteriorated kidney function groups. In recipient with AKI stage 3, higher serum sST2 levels were observed compared with recipients without history of AKI. In line with this finding, serum samples from recipients with HRS showed higher serum sST2 concentration. In recipients with severely decreased liver function (30< MELD score), higher serum sST2 level was measured compared with recipients with preserved liver function (MELD score <20). Conclusions: The increased level of serum sST2 reflected not only kidney function but also liver function. And elevated serum sST2 levels were measured in recipients with severe AKI or HRS.