Transthyretin has been proposed as a nutritional index to screen for malnutrition and monitor the metabolic response to dietary intervention. In the presence of inflammation, circulating transthyretin levels drop regardless of optimal caloric intake. In this case, due to its rapid turnover, the pattern of transthyretin, monitored by means of repeated measures, could indicate the metabolic status (catabolism vs. anabolism). The aim of this review is to investigate the possible role of transthyretin as a nutritional parameter in organ transplantation. The literature on nutritional assessment in transplantation was reviewed and all the data regarding circulating transthyretin levels were analyzed. It appears that, on the one hand, the transthyretin level reflects closely dietary manipulations; on the other hand, it is affected by the inflammatory status. Consequently, interpretation could be difficult during the acute phase immediately after the transplant. Moreover, the role of transthyretin in monitoring the hepatic synthetic function in liver transplant is discussed. In conclusion, transthyretin is a reliable indicator of nutritional status in transplant candidates and potentially useful in the post-transplant phase if the inflammatory status is taken into account.