Illustrated descriptions of three new free-living nematode species: Halalaimus minimus sp. nov., Halalaimus vietnamicus sp. nov. and Halalaimus orientalis sp. nov. are given. These species, belonging to the species group ? 1 of the genus Halalaimus, were found in the soil under mangrove vegetation in Vietnam. The review of this species group and dichotomy key for identification of males are provided.