Soon Spartans accused Themistocles of treasonable intrigues with Persia. Subsequently he was proclaimed a traitor in Athens and all his property was confiscated.

As a bitter irony, Themistocles could only find shelter at his enemy whom he fought for so many years. Artaxerxes I, successor of Xerxes I, offered him asylum and took Themistocles under his protection. Artaxerxes even made Themistocles a governor of the province of Magnesia in Asia Minor. He probably was well received in Magnesia and showed his talents there too, because Magnesians worshiped Themistocles as a god.

From what we know, Themistocles died of illness in Magnesia , when he was sixty five. He was probably a broken-hearted man, because there were persistent rumors that his death was not of natural causes but that he committed suicide by taking poison.