The Psidium guava Linn leaf extract as mouthrinse has been suggested to be used against toothache, and also has suggested effect against diarrhea and vomitting, as well as anti spasmodic and rheumatic symptoms, anti inflammation, anti piretic, analgetic, and anti bacterial activity. However, to consider potential side effects, this work aimed to test the acute toxicity of guava leaf extract. For this purpose guava leaf extract was given orally to groups of ten mice each at a doses of 1.25g, 2.5, 5, 10 and 21 g/kg body weight in a suspension with CMC Na 0,5%. Ten mice were used as control with a dose of 1 ml CMC Na 0,5%. The results suggest no acute toxicity to mice, since even the biggest dose given (show no measurable) value of LD 50. It could be concluded that guava leaf extract shows no acute toxicity to mice at tested concentrations.