Identification of species within the family Phytoseiidae is of primary importance for biological control programs. However, considerable disagreements between authors are often observed concerning the placement of species in genera. Moreover, considering the small number of available morphological characters and the poor knowledge of their reliability for species diagnostics, synonymies between several species could be questioned. This study aims to provide a taxonomic revision of a genus belonging to the sub-family Typhlodrominae: Neoseiulella Muma. Whereas the last revision of this genus (carried out in 1996) took into account 26 valid species, we propose now to include 47 species in the genus Neoseiulella based on type material observations. At first, three species (Neoseiulella eiko, N. eleglidus and N. schusteri) have been excluded from this genus, as their morphological attributes do not match the morphological characters which define the genus. Secondly, we also think that another species placed in the genus Typhlodromus (Anthoseius): T. (A.) elisae, has to be included in the genus Neoseiulella. Finally, several synonymies have been analysed and we conclude that: (i) N. aceri is a synonym of N. squamiger and provisionally of N. aceris, (ii) N. tiliarum is a synonym of N. formosa, (iii) N. transitans is a synonym of N. prunus, and provisionally of N. vollsella, (iv) N. manukae is a synonym of N. glenfieldensis and (v) Neoseiulella tuberculata, N. sexapori and N. arutunjani are considered valid specific entities. A new synonymy between Neoseiulella nesbitti and N. armidalensis is also proposed. A standardised re-description of all the species of the genus is proposed and a key to the species for the adult females is provided. This study also gives an exhaustive compilation of all available information concerning the geographical distribution of species of Neoseiulella and their plant supports.