The Waratahs recovered from their loss to the Brumbies last week by beating the Rebels 32-8 with a bonus point at Allianz Stadium in Sydney.
The Waratahs outscored the Rebels by foour tries to one after leading 11-8 at half time.
The result means that the Weary Dunlop Shield returns to Sydney with the Waratahs.
Waratahs fullback scored two tries in the match taking his tally to eight for the season.
Folau's second-half tries clinched the Waratahs' third bonus-point win. The Waratahs took an 11-8 lead to halftime after an indecisive first spell but tries to Folau and Peter Betham in the first eight minutes of the second half gave them breathing space.
Folau then earned the bonus point with his second try seven minutes from fulltime.
Both of Folau's tries came after breaks and inside passes from man of the match Kurtley Beale.
Beale made a line break and delivered an inside pass to Folau to set up the first try in the 48th minute, and again split the defence then slowed and held the ball up under pressure to lay on the second.
"It was a tough game to be honest," Waratahs captain Dave Dennis said.
"They put a lot of pressure on us in that first half.
"Going into halftime it was a very even contest but we just talked about sticking to our game in the second half, and to come away with four tries was a very pleasing effort."
No. 8 Dennis was part of a highly effective loose forward trio with openside Michael Cooper and former Springboks flanker Jacques Potgeiter, who was hugely industrious as was lock Will Skelton.
Beale gave the Waratahs the key that unlocked the Rebels' defence, which had been extremely resilient through the first half.
Winger Alofa Alofa gave the Waratahs the lead after only three minutes with a try which followed a break by Potgeiter but the Rebels hit back with a try to captain Scott Higginbotham, his 25th in Super Rugby.
Bernard Foley kicked two penalties for the Waratahs and Bryce Hegarty one for the Rebels, leaving a three-point gap between the teams at the interval.
The Waratahs took the game away from Melbourne with the tries to Betham and Folau immediately after the restart. They almost had another, through Dennis, but that was denied when television replays showed a knock-on by Potgeiter in a preliminary phase.
The Rebels again resisted strongly through the middle of the second half and handling errors prevented the Waratahs scoring again until the 73rd when Folau's second try gave them the comfort of a bonus point.
The Rebels remained without a win in Sydney in Super Rugby, though they competed strongly at times.
"It's disappointing," captain Higginbotham said. "They defended well. "
"We worked hard and kept getting into their tryline area but just let ourselves down and let them off the hook."
Final Score Waratahs 32 (11) Rebels 8 (8)
Tries - A. Alofa, P.Betham, I.Folau 2
Pen - B.Foley 2
Con - B.Foley 3
Tries - S.Higginbotham.
Pen - B.Hegarty
Cards - A.Roberts (53rd min yellow)
Referee: Jaco Peyper
Assistant Ref 1:Rohan Hoffmann
Assistant Ref 2:Graham Cooper
TMO : George Ayoub
1. Sekope Kepu 2. Tatafu Polota Nau 3. Paddy Ryan 4. Will Skelton 5. Kane Douglas 6. Jacques Potgieter 7. Michael Hooper 8. Dave Dennis (c) 9. Nick Phipps 10. Bernard Foley 11. Peter Betham 12. Kurtley Beale 13. Adam Ashley-Cooper 14. Alofa Alofa 15. Israel Folau
Replacements from: 16. Tolu Latu 17. Jeremy Tilse 18. Benn Robinson 19. Wycliff Palu 20. Stephen Hoiles 21. Brendan McKibbin 22. Rob Horne 23. Matt Carraro24. Pat McCutcheon 25. Jonno Lance
1. Toby Smith,2. Pat Leafa,3. Paul Alo-Emile,4. Hugh Pyle,5. Luke Jones,6. Sean McMahon,7. Scott Fuglistaller,8. Scott Higginbotham (C),9. Luke Burgess,10. Bryce Hegarty,11. Tom English,12. Mitch Inman ,13. Tamati Ellison,14. Lachlan Mitchell ,15. Angus Roberts
Replacements : 16. Shota Horie,17. Max Lahiff,18. Cruze Ah-Nau ,19. Cadeyrn Neville,20. Colby Fainga'a,21. Ben Meehan,22. Male Sa'u ,23. Tom Kingston