Hymenagaricus mlimaniensis Mwanga & Tibuhwa sp. nov. is described from Dar es Salaam Mlimani Main Campus in the semi protected natural tropical forest left in the Dar es Salaam city. The species superficially looks like Agaricus and its differences to the closest taxa in Hymenagaricus genus is both morphologically and genetically presented. The species is distinctively characterized from the closest H. pallidodiscus Reid & Eicker and H. alphitchrous (Berk. & Broome) Heinem by having the distinctive pink-reddish colour of the disc, more white diminutive fibril on the pink-reddish background, lack of developed cortinate veil, possession of smooth margin and microscopically, the presence of clamp connections which are lacking in the two closest taxa. This study thus, describe H. mlimaniensis sp. nov. as a new species in Hymagaricus genus based on both macro-micromorphology and molecular markers.