Trapa pseudoincisa Nakai, an aquatic plant, was extracted with 80% aqueous MeOH, and the concentrated extract was successively partitioned with EtOAc, n-BuOH, and $H_2O$. The EtOAc fraction gave three compounds, which were isolated through the repeated silica gel and ODS column chromatographies. Based on the spectroscopic data obtained from NMR, MS, and IR, the chemical structures of the compounds were determined as cycloeucalenol (1), ursolic acid (2), and 2${eta}$,3${alpha}$,23-trihydroxyurs-12-en-28-oic acid (3). These triterpenoids were isolated for the first time from Hydrocaryaceae plants including T. pseudoincisa NAKAI.