Rhea had also participated in the Gigantomachy

The Gigantomachy was a conflict between the Olympian gods and the Giants or Gigantes, sons of Uranus and Gaia. They all desired to topple the existing order and usurp it to usurp themselves as the new universe's rulers.

When the giant Alcyoneus stole the god Helios' livestock, the conflict began. According to a prophecy, gods could only defeat giants with the help of a mortal. Gaia searched for the plant that would protect the giants. Zeus, however, seized every plant for himself, not sparing a single one.

Alcyoneus, who didn't perish in his own country, was fought by Heracles during the conflict. Heracles killed the giant by dragging him out of his territory on the counsel of Athena. Dionysus similarly killed Eurytus as how Hermes killed Hippolytus. When Python and his brother Enceladus were put in prison, the conflict came to an end.

Rhea took part in the conflict and assisted the Olympians in overcoming the giants. However, it is unknown how she carried out her duties during the conflict.