Apollodorus makes Phineus a brother of Cepheus and records that Andromeda had first been betrothed to him before Perseus rescued her from the rock. A related genealogical strand, preserved in later handbooks, makes Phineus a son of Belus by Anchinoe and thus brother also to Aegyptus and Danaus as well as Cepheus.

The betrothal places him at the centre of the Andromeda wedding crisis: Perseus claims the princess as the reward for killing Cetus; Phineus asserts a prior claim and gathers armed followers against the hero.

Apollodorus gives the episode in a single summary line: Phineus plotted against Perseus at the marriage feast; Perseus discovered the conspiracy and showed the Gorgon's head, turning Phineus and his fellow conspirators to stone.

Ovid's Metamorphoses supplies the only extensive ancient narrative. Phineus bursts in with a spear while Perseus is recounting his deeds; Cepheus rebukes his brother for having done nothing to save Andromeda, but battle follows. Perseus finally unveils Medusa's face; most attackers freeze at once. Phineus, gaze averted, begs for life, but Perseus forces him to look and he too becomes stone. Hyginus likewise lists Phineus among those who opposed the marriage after Andromeda was freed. The affair may also have formed part of Euripides' lost Andromeda.

This Phineus ends as a statue among the wedding guests. He must not be merged with Phineus of Thrace, the prophetic king whom the Boreads freed from the Harpies and who guided the Argonauts past the Symplegades. The atlas keeps them apart as `phineus-ethiopia` and `phineus-thrace`.