Neoseiulus HUGHES, 1948 is currently one of the largest genus of Phytoseiidae Berlese. Neoseiulus demitei sp. nov., a new species of phytoseiid mite from Rio Grande do Sul State, Brazil, is illustrated and described based on specimens collected on Tibouchina sp. (Melastomataceae) plants. This new species differs from others by having most of propodossomal setae reaching the base of nearby setae and a constriction of ventrianal shield at level of preanal pores. Nevertheless, this new species is the first of the species subgroup kennetti described from Brazil. A key of Neoseiulus species reported in Brazil is also included.