Israel Folau scored a hat-trick as Waratahs ended a three-match losing streak and inflicted a debut defeat on new Cheetahs coach Franco Smith in an entertaining 58-33 victory in Bloemfontein.
Michael Cheika's Waratahs are top of the Australia conference. Waratahs and Brumbies both have 47 points, but the former have one more win.
Waratahs ran in nine tries in total, with Folau helping himself to a double in a high-scoring first half that saw the visitors lead 29-21.
The Australia international rounded off his hat-trick on the hour when he scored despite an obvious trip from Rayno Benjamin - who was sin-binned for his actions.
Victory for the Waratahs guarantees at least a play-off spot, as New Zealand side Crusaders miss out for the first time since 2001 despite beating Blues 34-11.
Crusaders ran in four tries, but they can no long muscle their way into sixth place.
It was a different story for Chiefs, though, as they dominated Reds in a 24-3 win to extend their season.
Chiefs had not won on Australian soil since 2013, but scores from Bryce Heem, Liam Messam and Charlie Ngatai ended that run. Will Genia - playing his last home match for Reds before leaving for Stade Francais - was denied a scoring send-off when he dropped the ball in the tackle just before half-time.
Bulls' hopes of reaching the play-offs were extinguished as they surrendered a 10-point lead in a 21-20 away loss to Rebels, who beat the Pretoria franchise for the first time.
The visitors led 17-7 by the 30th minute, but tries from Sean McMahon, Jack Debreczeni and Lopeti Timani put Rebels in control.
Bulls were left feeling aggrieved when Burger Odendaal appeared to ground a try just after the hour, but the television match official deemed otherwise.
Stormers clinched the South Africa conference in Super Rugby despite being held to a late draw by domestic rivals Lions, while Waratahs and Chiefs confirmed their play-off places on Saturday.
Allister Coetzee's Stormers had just a three-point lead over Lions heading into the contest at Newlands Stadium, meaning victory for the visitors would have left the Stormers needing a win in their final match.
It appeared as though Stormers were en route to victory when leading by seven points heading into the closing stages, but Malcolm Marx's 76th-minute try, converted by Marnitz Boshoff saw the game end 19-19.
However, Lions have a bye next week, meaning Stormers cannot be caught in the South Africa conference. The latter's spot in the play-offs is therefore secured and Lions can no longer qualify.
Nic Groom, Dillyn Leyds and Nizaam Carr all scored for the Stormers - but the draw did deal a blow to their chances of getting a home semi-final.