He was son of Megabyzus, who helped Darius I in his ascension. When Babylon revolted against the rule of Darius I, Zopyrus devised a plan to regain control of the vital city. By cutting off his own nose and ears, and then having himself whipped, he arrived at the court of Darius. He told the ruler of his plan: He would go before the people of Babylon and proclaim himself an exile punished by Darius. Gaining the Babylonians' trust, Zopyrus soon became commander-in-chief of their army, allowing him to weaken the city's defenses. With this, Darius' armies victoriously reconquered the city. Zopyrus was made satrap.
The veracity of this story is debatable. First, the story resembles Homer's description of Odysseus, who spied on Troy after mutilating himself. Second, no cuneiform sources mention Zopyrus as satrap of Babylon.
According to Herodotus, Zopyrus had a son named Megabyzus.