Lesions associated with storage of red blood cells (RBC) in different anticoagulants have been well described in mammals, but not in reptiles to date. The objectives of this study were to document biochemical changes of American alligator (Alligator mississippiensis) packed RBC stored in citrate–phosphate–dextrose–adenine (CPDA-1) and acid–citrate–dextrose (ACD) anticoagulants over the course of 35 days and to describe qualitative and quantitative morphologic changes over 295 days. Blood samples were collected via the occipital sinus from 6 captive-born American alligators of mixed sex (1 male, 5 females). Spun packed cell volume (PCV), total solids, and blood lead levels were analyzed with the use of heparinized blood on Day 0. Samples in CPDA-1 and ACD were stored at 4°C (39.2°F) and the following parameters serially evaluated at varying time points until Day 35: blood culture, blood gas analysis, PCV, methemoglobin, osmotic fragility, and morphologic evaluation by light and transmission electron microscopy. Further assessment of osmotic fragility on Days 45 and 60 and morphologic evaluation by light microscopy on Days 60 and 295 were performed. One positive blood culture in the ACD anticoagulant group was noted on Day 0, but all were negative on Day 35. Biochemical changes included statistically significant increases in potassium and lactate concentrations in both anticoagulants from Day 0 to Day 35. Spun PCV decreased significantly from Day 7 to Day 35 in both anticoagulants and methemoglobin decreased significantly from Day 0 to Day 35 in ACD. Osmotic fragility showed no significant change from Day 2 to Day 35 or between anticoagulants, but was significantly different between Day 2 and Days 45 and 60 in the CPDA-1 group. Degenerative changes of RBC on blood film evaluation included nuclear pyknosis, erythroplastid formation, RBC swelling, RBC shrinkage and cytoplasmic membrane blebbing. There were no significant abnormal morphologic findings by transmission electron microscopy. The results of this study indicate that American alligator erythrocytes can be stored as packed RBC for at least 35 days in CPDA-1 or ACD.