Two new species of black flies, Simulium mainitense and S. tukurongense, are described from Palawan, the Philippines. Both species are placed in the Simulium nitidithorax subgroup of the Simulium tuberosum species-group of Simulium (Simulium). They are characterized by the female sensory vesicle of medium length, pupal thorax covered with round tubercles, and anterodorsal trichomes on the pupal thorax longer than frontal trichomes. This combination of characters separates these two new species from S. quasifrenum Delfinado, the only previously known member of the S. nitidithorax subgroup from Palawan, and nine other related species from Sabah, Sarawak, Peninsular Malaysia and India. Simulium mainitense sp. nov. is distinguished from S. tukurongense sp. nov. in the female by the somewhat larger body size, and greater length ratio of the labrum against the clypeus; and in the pupa by the much longer gill filaments.