© 2018 American Society for Veterinary Clinical Pathology Background: Hematologic and serum biochemical reference values obtained from captive or free-ranging wildlife populations may not be comparable as there can be significant variations due to preanalytic and analytic differences, including methods of capture and restraint, overall management in captivity including diet and composition of animal groups, and analytic methods being used. Hematology and serum biochemistry have never been studied in captive or free-ranging populations of Sechuran foxes (Lycalopex sechurae). Objectives: The purposes of the study were to determine hematologic and serum biochemical RI in Sechuran foxes and to explore differences in these variables related to sex and overall life circumstances. Methods: Blood samples were obtained from 15 free-ranging and 15 captive Sechuran foxes. Hematology variables were assessed by blood smear examination and automated analyzer methodology. Serum biochemical analysis was performed by automated analyzer methodology. Descriptive statistics were calculated for each variable. Data obtained from free-ranging and captive groups were statistically compared and RIs were calculated. Results: Captive Sechuran foxes had significantly (P <.05) higher MCH, MCHC, and eosinophil counts and significantly lower band neutrophil counts than free-ranging foxes. Free-ranging Sechuran foxes had significantly (P <.05) higher serum lipase and globulins and significantly lower albumin, total bilirubin, and indirect bilirubin than captive foxes. Conclusions: These findings suggest that there are hematologic and serum biochemical differences between captive and free-ranging Sechuran fox populations. Hence, such differences should be considered when using these variables to assess the health status of this species.