Abstract: The histology of the spleen, lymph nodes, Gut-associated lymphoid tissue (GALT) and Bronchus-associated lymphoid tissue (BALT) are described for samples collected opportunistically from healthy and mycobacteria-affected specimens of the endangered marsupial Lagorchestes hirsutus, the Rufous Hare-wallaby. The structural elements, organization and distribution of T and B lymphocytes determined by immunohistological techniques using species cross-reactive antibodies in the lymph nodes, spleen and GALT of this species demonstrated lymphoid cell distributions that were consistent with other marsupial and eutherian mammals. The tissues of animals identified as acid-fast positive displayed immunopathology consistent with the responses to intracellular bacteria displayed in some eutherian mammals and included the presence of focal lesions, giant cells in the lung and lymphoid aggregations situated adjacent to blood and airway vessels. This is the first study to describe the lymphoid tissue of this rare macropod species and the first to document the tissue bed response to mycobacteria.