At the request of Thetis, Lycomedes concealed Achilles in female disguise among his own daughters. At Lycomedes' court Achilles had an affair with Deidamia, which resulted in the birth of Neoptolemus (Pyrrhus). As Odysseus drew Achilles out of his disguise and took him to Troy, Neoptolemus stayed with his grandfather until he too was summoned during the later stages of the war.
Plutarch says that Lycomedes killed Theseus who had fled to his island in exile by pushing him off a cliff for he feared that Theseus would dethrone him, as people of the island treated the guest with marked honor. Some related that the cause of this violence was that Lycomedes would not give up the estates which Theseus had in Scyros, or the circumstance that Lycomedes wanted to gain the favour of Menestheus.