Antilochus was the son of King Nestor either by Anaxibia or Eurydice. He was brother to Thrasymedes, Pisidice, Polycaste, Perseus, Stratichus, Aretus, Echephron, and Peisistratus.

One of the suitors of Helen, Antilochus accompanied his father Nestor and his brother Thrasymedes to Troy. When fighting resumed after the aborted duel of Paris and Menelaus, Antilochus was first to kill a Trojan captain (Echepolus). Though the youngest among the Greek princes, he commanded the Pylians and performed many deeds of valour. He was a favorite of the gods and a close friend of Achilles.

Antilochus was commissioned to tell Achilles of Patroclus's death. While they lamented together, Antilochus held Achilles's hands for fear that he would cut his own throat. At the funeral games of Patroclus, Antilochus finished second in the chariot race — after an aggressive pass that drew a quarrel with Menelaus, which Antilochus defused by deference — and last in the foot race.

The epic cycle of the Aethiopis details Antilochus' death. When Nestor was attacked by Memnon, Antilochus sacrificed himself to save his father, fulfilling an oracle that had warned to "beware of an Ethiopian." Achilles then killed Memnon to avenge him. In later accounts Antilochus was slain by Hector, or by Paris in the temple of the Thymbraean Apollo together with Achilles.

Antilochus' ashes, along with those of Achilles and Patroclus, were enshrined in a mound on the promontory of Sigeion. In the Odyssey the three are represented as always united in the underworld; according to Pausanias they dwell together on the island of Leuke.