AbstractTwo new glycerolipids, syngaculipids A and B (1 and 2), one first naturally occurring metabolite (8), together with five known compounds (3–7) were isolated from the AcOEt fraction of Syngnathus acus L. (Hai‐Long). Their structures were elucidated by comprehensive spectral analyses involving UV, IR, MS, 1D and 2D NMR spectra and ECD calculations. All the isolated compounds were evaluated for their cytotoxicity against A549 and HCT‐116 cell lines. Compound 8 exhibited moderate cytotoxicity with IC50 values of 34.5 and 38.9 μM on the A549 and HCT‐116 cell lines, respectively.