This is the first study designed to explore behavioral effects of the water extract of the moss Rhodobryum ontariense (ROE). Experimental adult animals received intraperitoneal injections of ROE (50–400 mg/kg; vs. saline) 45 min before behavioural evaluation. Motor effects of ROE were estimated in male mice using the open field test (OFT), whereas the elevated plus maze (EPM) model of anxiety was applied on male rats. Single ROE treatments significantly decreased motor activity of mice in OFT (p<0.001) by reducing both the percentage of activity time and the distance travelled in 15 min. Also, ROE in rats significantly increased (p<0.05) the percentage of time spent in open arms and the number of open-arm-entries during 5 min, which was similar to the actions of diazepam in rats (1 mg/kg). These results demonstrated that ROE produced motor sedation and anxiolytic-like effects in rodents.