The essential oil or extract of Lemon myrtle (Backhousia citriodora F. Muell.), belonging to the family Myrtaceae and the genus Backhousia, exhibits anti-inflammatory and antioxidant properties. However, limited information exists on the safety of water extracts from its leaves. The present study aimed to assess the safety of lemon myrtle water extract as a functional food by performing genotoxicity studies and repeated-dose oral toxicity. Although the bacterial reverse mutation test (Ames test) yielded positive results, in vivo mammalian erythrocyte micronucleus and alkaline comet assays yielded negative results. In a 28-day oral toxicity study, the extract was orally administered to male and female Crl:CD rats at doses of 0, 250, 500, and 1000 mg/kg bw/day. Notably, the extract induced no adverse effects, and the no-observed-adverse-effect level was 1000 mg/kg bw/day in male and female rats. Despite its genotoxicity in vitro, the extract did not exhibit genotoxicity in vivo. Moreover, no signs of toxicity were observed in the general toxicity study. Overall, these results suggest that lemon myrtle water extract does not pose a substantive genotoxic risk at practical oral exposure levels.