Foliicolous microthyriaceous fossil fungus Palaeoasterina siwalika gen. et sp. nov. is described from the Siwalik sediments (Middle Miocene) of Darjeeling foothills, eastern Himalaya. Both vegetative and reproductive phases of the fossil fungus are preserved. The characteristics of septate, hyphopodiate, superficial mycelial reticulation, simultaneous bipolar germination of ascospores and dimension of vegetative and reproductive structures of the fossil form are closely comparable with the extant fungus Asterina viz., A. aporosae Hansf. var. cylindrica Kar and Ghosh growing in tropical humid climate. The occurrence of Palaeoasterina in the Siwalik foothills suggests tropical humid climate with high rate of precipitation in the area during Neogene Period.