The Waratahs mounted a spirited late comeback to give themselves a shot at the end, but were unable to break through after the siren, suffering another heartbreaking defeat 31-26 in the closing moments.
The Highlanders dominated the opening half, taking control with a commanding 28-7 lead at halftime.
However, Joseph-Aukuso Suaalii inspired the visitors’ fightback, while a red card to Jona Nareki helped set up a tense finish.
Sid Harvey crossed with two minutes remaining, but the rally fell just short as the hosts held on to keep their finals hopes alive.
In other results, the Hurricanes thrashed Moana Pasifika 50-17, while the Brumbies defeated the Force 32-15.
