The cyclopoidApocyclops royi(Lindberg 1940) and the calanoidPseudodiaptomus annandalei(Sewell 1919) are 2 tropical copepods suspected of having the capability to biosynthesize the physiologically important n-3 polyunsaturated fatty acids (n-3 PUFAs) eicosapentaenoic acid (C20:5n-3, EPA) and docosahexaenoic acid (C22:6n-3, DHA). We demonstrated this suspected ability using¹³C₁₈α-linolenic acid (C18:3n-3, ALA) fed to the copepods through liposomes and a subsequent fatty acid (FA) analysis by GC-MS at 3 different time points (0, 24, and 48 h). Two different diets were applied post liposome exposure: baker’s yeastSaccharomyces cerevisiaeand the microalgaDunaliella tertiolecta.For both copepods, further elongated and desaturated¹³C n-3 PUFAs were found at all time points. At T_48h,A. royiandP. annandaleicontained¹³C-labelled DHA contents (±SD) of 1.3 ± 0.2 and 0.7 ± 0.3 µg¹³C-FA mgC_copepod^-1when fed baker’s yeast, respectively, and 1.2 ± 0.1 and 1.6 ± 0.5 µg¹³C-FA mgC_copepod^-1when fedD. tertiolecta, respectively, with significant differences observed only betweenP. annandaleidiet treatments. The¹³C-labelled EPA content ofA. royiandP. annandaleiat T_48hwas 0.6 ± 0.4 and 0.7 ± 0.4 µg¹³C-FA mgC_copepod^-1when fed baker’s yeast and 0.8 ± 0.2 and 0.3 ± 0.1 µg¹³C-FA mgC_copepod^-1when fedD. tertiolecta, with significant differences only between copepods fedD. tertiolecta.A. royiandP. annandaleiexhibited an ability to produce n-3 PUFAs from the precursor ALA in comparatively large quantities. This ability enables these 2 species to inhabit habitats characterized by PUFA-poor particulate material.