Phytochemical study on the methanol extract of the marine sponge Xestospongia testudinaria (Lamark, 1815) led to the isolation of one new ((6Z,8E,13E,15Z)‐6,14,16‐tribromo‐5,10‐dihydroxyhexadeca‐6,8,13,15‐tetraenoic acid named xestospongiene VN1, 1) and nine known brominated polyunsaturated compounds, xestospongiene z5 & z6 (2), xestospongiene z9 & z10 (3), xestospongiene S (4), xestospongic acid (5), xestospongic acid methyl ester (6), (13E,17E)‐18‐bromo‐octadeca‐13,17‐diene‐5,7,15‐triymoic acid (7), xestospongiene I & J (8), xestospongiene K & L (9), and xestospongiene C & D (10). The chemical structures of these compounds were elucidated by extensive spectroscopic analyses including HR‐ESI‐MS, 1D and 2D NMR, circular dichroism, and by comparison of the spectral data with those of previously reported data. This is the first report of these compounds from Vietnamese marine sponge X. testudinaria.