Cold-stunned loggerhead sea turtles (Caretta caretta) strand annually in the northeastern United States and are admitted to rehabilitation facilities when rescued alive. Hematologic and plasma biochemical data were retrospectively evaluated from 133 cold-stunned loggerhead turtles that were admitted for rehabilitation between 2008 and 2016. Convalescent data were compared with initial data for 24 turtles for which paired data were available. Convalescent values for white blood cell count, heterophil count creatine kinase, lactate dehydrogenase, glucose, and uric acid were significantly lower than initial values, whereas convalescent eosinophil count, alanine aminotransferase, aspartate aminotransferase, albumin, gamma-glutamyl transferase, total protein, globulin, blood urea nitrogen, calcium, phosphorus, chloride, and potassium were significantly higher. Results indicate that cold-stunned loggerhead turtles may be affected by dehydration, reduced renal function, cellular injury, deranged metabolic status, and activation of the adrenocortical stress response. Specific derangements associated with mortality could not be statistically characterized because only four turtles died.