After the return of the Argonauts his sisters were seduced by Medeia to cut their father in pieces and boil them; and Acastus, when he heard this, buried his father, drove Jason and Medeia, and according to Pausanias (vii. 11) his sisters also, from lolcus, and instituted funeral games in honour of his father.
When Peleus refused to listen to her addresses, she accused him to her husband of having attempted to dishonour her. (Apollodorus iii) Acastus, however, did not take immediate revenge for the alleged crime, but after he and Peleus had been chasing on mount Pelion, and the latter had fallen asleep, Acastus took his sword from him, and left him alone and exposed, so that Peleus was nearly destroyed by the Centaurs. But he was saved by Cheiron or Hermes, returned to Acastus, and killed him together with his wife.