The yellow-marginated box turtle (Cuora flavomarginata) is critically endangered and very few studies have been performed to aid the conservation effort. This study reports the first complete analysis of blood parameters for this species and will provide a reference for future conservation studies. Hematology and biochemistry reference range values were established from 52 (18 males and 35 females) clinically healthy yellow-marginated box turtles (C. flavomarginata). In order to investigate the gender and seasonal differences in these ranges, blood samples were collected from the jugular veins of the turtles in January, April, July, and October to represent the four seasons. To detect significant variation (P < 0.05), data were analyzed using repeated measurements of analysis of variance. Significant gender differences were observed in red blood cell mass parameters, absolute eosinophils, absolute monocytes, alkaline phosphatase, aspartate aminotransferase, blood urea nitrogen, calcium, uric acid, cholesterol, creatine kinase, glucose, phosphorus (P), total protein, and triglycerides. Marked seasonal variations were noted in red blood cell mass parameters, absolute monocytes, albumin, alkaline phosphatase, aspartate aminotransferase, blood urea nitrogen, uric acid, creatine kinase, creatinine, glucose, P, and triglycerides. Primary reasons for the differences between gender and season were associated with reproduction and temperature change. Cuora flavomarginata has lower alanine aminotransferase values compared with other chelonians.