Unlike most other ant species, pharaoh ants have many queens in a colony. The ants develop in several colonies in nests and live amicably together. The colonies form one big aggregate nest that may contain many workers–anywhere from tens to hundreds of thousands. As the nest becomes larger and larger, the workers will evacuate the nest along with eggs and larvae to begin building new colonies. These migrations may occur at any time of the year, whenever a nest begins to become overcrowded. Since the ants are relatively unaffected by the seasons, sexual forms are produced and found throughout the year. A young queen may lay up to 300 eggs. The eggs hatch into legless larvae in 7 ½ days and are fed by the queen through the process of trophallaxis. Unless searching for food herself, the queen will stay in the nest and rely on workers to find nourishment. After 18 days, the larvae are fully grown. Then, they enter a 9-day pupal stage. The pupal stage leads to the worker stage, which takes approximately 38 days to complete. The worker pharaoh ants are sterile females. Their duties to the nest include providing nourishment for the young and the queens. Also, they work to keep the nest sanitized. Fertile males and females are occasionally produced from large, well-fed larvae.

Ant mating usually takes place in wall spaces and crevices of infested buildings. This mating is never observed due to the fact that the sexual forms are unable to fly.