Workers are 1/16 to 1/8 inch long and monomorphic. The body is dark in color, antenna has 12 segments without a club, thorax is uneven, and pedicel has 1 hidden node. There is no circle of hairs at the anal pore. A distinctive characteristic of this species is the rotten odor when crushed.

Odorous house ants can develop extremely large colonies but tend to maintain colonies of only several thousand workers with many queens. Swarmers appear in May through July. They most prefer sweets but will also feed on dead insects and grease.

Odorous house ants will nest indoors near sources of moisture and warmth, in voids, but also in termite-damaged wood. They nest outside under lumber, firewood, and debris and may then trail indoors to forage. These ants will tend aphids for the honeydew and can be forced indoors when aphids are exterminated or die back because of weather (cold or drought)