Two known bromotyrosine alkaloids were isolated for the first time from the methanol extract of Vietnamese marine sponge lanthella basta. Their structures were identified as purealidin R (1) and fistularin-3 (2) by spectroscopic methods and in comparison with the previously reported data. Compound 1 showed strong cytotoxicity against 8 human cancer cell lines as HepG2, KB, LV-I, MCF7, LNCaP, SW480, MKN7, and HL-60 with the IC50 values ranging from 3.27 to 6.08 ug/mL, whereas 2 had moderate to weak or no cytotoxicity against the human cancer cell lines.