Although Mesobuthus scorpions in China have become endangered in recent years, they are largely underinvestigated. Even the baseline data on their distributions are lacking. Here the geographical distributions of two Mesobuthus scorpions in China are provided through a combined study of systematic field surveys and GIS-based ecological niche modeling using 227 surveyed point occurrence data across an area of ca. 2800 × 1700 km2 and validated historical records. Mesobuthus martensii (Karsch 1879) appears to be restricted to latitude south of 43°N and the north side of the Yangtze River, bordered by the Helan Mountains and the Tengger and Mo Us sand desert in the west and limited by the sea in the east. Mesobuthus eupeus (C.L. Koch 1839) reaches the east side of the Helan Mountains and the west edge of the Loess Plateau, extending westward along the northern slope of the Qilian Mountains and ultimately penetrating to the northern part of the Junggar Basin. The former is mainly found in semi-humid and humid regions while the latter is an arid and semi-arid dweller. The two species show a parapatric distribution on the whole with a contact zone formed at the boundary of their ranges across the big turning of the Yellow River in the central-western part of Inner Mongolia, Ningxia and the middle part of the Gansu Province. This pattern of distribution is shaped both by the fundamental ecological niche constraint of the species and possibly by the biological interactions between the two species. Some diagnostic features for the two species are also provided for quick identification.