Five tammar wallabies (Macropus eugenii) were injected intramuscularly with 10 mg/kg amoxicillin trihydrate. Serial blood samples were collected through to 26 hr postinjection. Plasma amoxicillin concentrations were measured using high-performance liquid chromatography. Pharmacokinetic parameters were estimated using noncompartmental analysis. The terminal half-life (1.77 ± 0.40 hr) was comparable to that previously reported in domestic small ruminants. Without intravenous kinetic data, it is unclear whether the terminal phase is elimination- or absorption-dependent; both scenarios have been reported in domestic species. Plasma concentrations of amoxicillin remained above a reported minimum inhibitory concentration (MIC) breakpoint for staphylococci and streptococci for at least 8 hr; the MIC breakpoint for enterobacteria and enterococci was never attained.