Microthrombi are often observed in the glomerular tufts of peri-transplant renal biopsies, and occult fibrin has been described in livers undergoing normothermic perfusion, with its presence associated with cholangiopathy and poorer transplant survival. To further examine the phenomenon, we measured D-dimers in the perfusates of kidneys and livers that were part of organ perfusion studies conducted by the Consortium for Organ Preservation in Europe. Both kidneys and livers were found to contain variable amounts of D-dimers. The need for dialysis in kidneys donated after circulatory death (DCD) was associated with higher levels of D-dimers in the hypothermic kidney perfusate. Higher amounts of D-dimers in the liver perfusate were associated with poorer liver transplant survival. There was no significant difference in D-dimer release from livers and kidneys between donors who died from head trauma, stroke, or hypoxia. Organs from donors who died by euthanasia had significantly fewer D-dimers. This study shows that occult fibrin is common in both livers and kidneys from deceased donors and has adverse consequences. The different D-dimer loads by donor cause of death suggest a donor origin for at least some of the occult fibrin.