This revision deals with the Zygothrica samoaensis species group, which includes 15 species, five of which are described as new to science. Two synonymies are proposed: Z. vietnamensis Grimaldi, 1990, as a junior synonym of Z. flavofinira Takada, 1976, and Z. britannia Grimaldi, 1990, as a junior synonym of Z. malaysiana Grimaldi, 1990. The samoaensis group is divided into three species subgroups: (i) the samoaensis subgroup, consisting of nine species, including a new species, Z. australiaensis sp. nov.; (ii) the fijiana subgroup of Z. fijiana Takada, 1976, and two new species, Z. triscutellaris sp. nov. and Z. bicornigera sp. nov.; and (iii) the leptorostra subgroup of Z. leptorostra Grimaldi, 1990, and two new species, Z. pimacula sp. nov. and Z. quintamaculata sp. nov. Supplementary information on geographic distribution is provided for some species, as well as a key to all species of the samoaensis group. Zygothrica kokodana Grimaldi, 1990, and Z. paleovitta Grimaldi, 1990, have closer affinity with the hirticornis and the quadrivittata species groups, respectively, and so are moved to the corresponding genus Hirtodrosophila.