Hematology is a routine component of clinical management in veterinary patients. Anticoagulant choice can profoundly influence morphologic assessment of erythrocytes, leukocytes, thrombocytes, and their subsequent quantification. Previous chelonian studies suggest that lithium heparin (LH) is a superior anticoagulant due to hemolysis resulting from dipotassium ethylenediaminetetraacetic acid (dEDTA) in some species. The aim of this study was to compare the effects of dEDTA and LH on hematologic values in Blanding's turtles (Emydoidea blandingii, n = 35), painted turtles (Chrysemys picta, n = 34), and common snapping turtles (Chelydra serpentina, n = 36). We collected samples from free-ranging turtles and immediately divided whole blood into LH and dEDTA tubes. Packed cell volume, total solids, erythrocyte sedimentation rate, white blood cell counts, and differential leukocyte counts were determined. Hemolysis was observed macro- and microscopically in dEDTA samples from painted turtles and common snapping turtles. Packed cell volume and heterophil:lymphocyte was lower and erythrocyte sedimentation rate was higher in LH samples from painted turtles (p, 0.05). In snapping turtles, the PCV, number of monocytes, and number of eosinophils was lower in LH samples (p, 0.05). In Blanding's turtles, the number of eosinophils and basophils was higher in LH samples, while heterophil counts were lower (p, 0.05). Anticoagulant choice created constant and proportional bias for multiple analytes in a species-dependent fashion. LH is the recommended anticoagulant for hematology in painted turtles and common snapping turtles. Either LH or dEDTA may be used in Blanding's turtles, though anticoagulant-specific reference intervals may be necessary.