Hematology is an important tool for the veterinary evaluation of reptiles. At this time, there are limited data on hematological reference intervals and physiological factors that influence hematological values in many reptile species, including the red-eared slider (Trachemys scripta elegans). The goal of this study was to establish subspecies-specific reference intervals for a single population of red-eared sliders from a lake in Southern Germany sampled on a single day in the fall. Lithium heparinized blood samples and blood smears were collected from 42 turtles and packed cell volume (PCV), hemoglobin, leukocytes, thrombocytes, and the differential blood count were evaluated. The results showed no significant differences between males and females, with the exception of the absolute monocyte count. The sex-independent calculated median values are: PCV 22.5%, hemoglobin 58.0 g/L, leukocytes 2.4 G/L, heterophils 0.51 G/L, eosinophils 0.82 G/L, basophils 0.19 G/L, lymphocytes 0.64 G/L, monocytes 0.01 G/L, and thrombocytes 12.16 G/L. The present study provides a basis for the evaluation of blood values in this commonly kept turtle species in order to facilitate the correct interpretation of blood results.