A red-necked male wallaby (Macropus rufogriseus) from a German zoo was presented for acute onset of severe neurological signs, including head tremor, lethargy, unresponsiveness, and weakness. Serum biochemical abnormalities included increased LDH- and AST-levels, hyperproteinaemia, and reduced ALT-, ALP-, and creatinine-levels. The wallaby was found serologically positive for Toxoplasma gondii by the indirect haemagglutination test. After initiation of therapy by subcutaneous injections of trimethoprim/sulfadoxin, amelioration of neurological signs was noted and after 10 days the affected wallaby recovered. T. gondii can be confirmed rapidly by serology, and immediate therapy may reduce clinical illness and fatality of the disease within captive macropods.