Population differences in body condition, parasitic burden, hematology, and serum biochemistry of free-living tammar wallabies (Macropus eugenii) are presented and compared to studies reporting values in captive tammar wallabies. The nutritional distinction in the composition and quality of the available vegetation on Garden Island produces 3 sub-populations that differ in their human disturbance, body condition, rates of reproduction, and survival, providing unique opportunities to examine condition-related health parameters in free-living wallabies. Our results show several hematology analytes (in particular, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration), all the measured serum biochemistry analytes (urea, creatinine, triglycerides, and albumin), and total gastrointestinal parasite burden are significantly associated with body condition (body mass index), providing reliable indices of wallaby condition and habitat quality. The means and standard errors for hematology analytes (in particular, hemoglobin, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration) and all serum biochemistry values for free-ranging wallabies lie below and outside of reference ranges for captive wallabies, despite the naval base sub-population benefiting from human modified habitats with a consistent availability of food. This indicates that free-ranging tammar wallabies may be suffering from some challenges that captive wallabies do not face. The hematology and serum biochemistry values coupled with body condition indices suggest wallabies in the south bush sub-population are under greater nutritional stress and suffering from prolonged malnutrition. Examining all parameters in a single year and across years would be beneficial to further investigate habitat differences driving this change to help distinguish if vegetative structure and associated nutritional deficiencies and/or disease are limiting this population. Health monitoring is an integral part of the management of both captive and free-living populations and the data presented here will serve as an effective management tool in assessing the health status of free-living tammar wallabies. © 2013 The Wildlife Society.