Malnutrition is common in end-stage liver disease, but a correction after transplantation is expected. Body cell mass (BCM) assessment using total body potassium (TBK) measurements is considered the gold standard for assessing nutritional status. The aim of this study was to examine the BCM and, therefore, nutritional status of long-term survivors after childhood liver transplantation. This was a longitudinal nested cohort study of patients undergoing transplantation at <18 years of age and surviving >3 years with ongoing review at our center. TBK measurements were obtained before transplantation and during long-term follow-up. BCM was calculated from TBK and was adjusted for the height raised to power p, which depended on sex (BCM/heightp). The effects of the age at transplant, linear growth impairment, a diagnosis of biliary atresia, and steroid use were assessed. Thirty-two patients (20 males) participated; 59% had biliary atresia. The median age at transplant was 2.11 years (range = 0.38-10.92 years). Posttransplant testing was performed at a median of 7.23 years (range = 3.28-14.99 years) when they were 10.12 years old (range = 4.56-20.77 years). This cohort attained mean z scores for height, weight, and body mass index of −0.41 ± 1.36, −0.26 ± 1.14, and 0.04 ± 0.99, respectively. BCM/heightp was reduced before transplantation but was further reduced after transplantation (P < 0.001) despite the normalization of height and weight. Weight recovery, therefore, likely came from increased fat mass and not BCM. Linear growth impairment was associated with a greater reduction in posttransplant BCM/heightp (P = 0.02). In multivariate analyses, only an older age at transplant predicted reduced posttransplant BCM/heightp (P = 0.02). The age at transplant, sex, steroid use, and underlying diagnosis did not predict changes in BCM/heightp after transplantation. In conclusion, weight recovery in long-term survivors of childhood liver transplantation is likely due to increased fat mass because BCM remains reduced. Nutritional compromise persists in long-term survivors of childhood liver transplantation. Liver Transpl 20:922–929, 2014. © 2014 AASLD.