In the Odyssey, she was the first person to recognize him after he returned home from the Trojan War, after he entered his own house as a guest of Penelope, disguised as a beggar. Euryclea bathed him and recognized him by a scar just above his knee, which he had received from a boar while hunting with his grandfather Autolycus. Odysseus stopped her from telling Penelope or anyone else of his true identity.
Euryclea also informed Odysseus which of his servant girls had been unfaithful to Penelope during his absence, conspiring with Penelope's suitors and becoming their lovers. He hanged the twelve that Euryclea identified.
Later Euryclea helps Penelope confirm that Odysseus has indeed returned. Penelope tells her to move the bed Odysseus built in their marriage-chamber; Odysseus tells Penelope that this is not possible as one of the legs of the bed is built into a live olive tree, a secret that only Odysseus and Penelope know, and Penelope finally accepts him.