While in Cilicia, Evagoras gathered the support of 50 followers and returned secretly in 410, to gain possession of the throne. Expecting an eventual Persian response to recapture Cyprus, he cultivated the friendship of the Athenians, and after Conon's defeat at the Battle of Aegospotami he provided him with a refuge. For a time he also maintained friendly relations with Persia, and secured the aid of Artaxerxes II for Athens against Sparta. He took part in the battle of Cnidus of 394 BC which he provided most of the resources for and in which the Spartan fleet was defeated thanks to his efforts, and for this service his statue was placed by the Athenians side by side with that of Conon in the Ceramicus. But relations between Evagoras and the Persians became strained. From 391 they were virtually at war. Aided by the Athenians and the Egyptian king Hakor (Achoris), Evagoras extended his rule over the greater part of Cyprus, crossed over to Asia Minor, took several cities in Phoenicia (including Tyre), and persuaded the Cilicians to revolt.
One result of the peace of Antalcidas (387), to which Evagoras refused to agree, was that the Athenians withdrew their support, since by its terms they recognized the lordship of Persia over Cyprus. For the next ten years Evagoras carried on hostilities single-handed, except for occasional aid from Egypt, which was likewise threatened by the Persians. The Persian generals Tiribazus and Orontes at last invaded Cyprus in 381 BC, with an army far larger than what Evagoras could command. However, Evagoras managed to cut off this force from being resupplied, and the starving troops rebelled. The war then turned in the Persian favor when Evagoras' fleet was destroyed at the Battle of Citium, and he was compelled to flee to Salamis. Here, although closely blockaded, Evagoras managed to hold his ground, and took advantage of a quarrel between the two Persian generals to conclude peace (376). Evagoras was allowed to remain nominally king of Salamis, but in reality a vassal of Persia, to which he was to pay a yearly tribute. The chronology of the last part of his reign is uncertain. In 374 he was assassinated by a eunuch from motives of private revenge.
According to Isocrates's panegyric, Evagoras was a model ruler, whose aim was to promote the welfare of his state and of his subjects by the cultivation of Greek refinement and civilization. Isocrates also states that many people migrated from Greece to Cyprus because of the noble rule of Evagoras. Other contemporary sources -- Diodorus Siculus 14.115, 15.2-9; Xenophon, Hellenica 4.8 -- are not as unrestrainedly complimentary.
Although Cypriots were Greeks and their language a dialect of Greek, the Arcadocypriot, they used to write in an older and more difficult system, called Cypriot syllabary. Evagoras has been called a pioneer of the adoption of the Greek alphabet in Cyprus in place of the older Cypriot syllabary.