Crassispira nigrescens is a species of small predatory sea snail, a marine gastropod mollusk in the family Pseudomelatomidae.
The length of the blackish, brown shell attains 8.5 mm. The shell contains 8 whorls, showing a beaded sculpture. The outer lip is very thick. The sinus is not very deep. The siphonal canal is very short.
This marine species occurs in the West Indies.