The Reds held on in Canberra to earn a 12-13 victory over the Brumbies which keeps their title hopes alive and tightens up the Australian Super Rugby conference.
The visiting Reds scored the only try of the match through Luke Morahan early in the first half and the Brumbies could have snatched it with a lat penalty but Zack Holmes missed a kick almost on full time.
While the victory keeps the Reds title defence alive the result may have come at some cost as Wallabies and Reds captain James Horwill had to leave the field after his knee was twisted at a ruck.
Reds coach Ewen McKenzie said after the match that Horwill has a hamstring injury and is unlikely to feature in the Wallabies first Test match - against Scotland - next month.
Australian Conference leaders the Brumbies have a five-point lead over the Reds who will pick up a guaranteed four points for their bye next weekend.
The Brumbies play the Rebels next weekend before taking a four-week break for the June internationals.
"We were very fortunate at the end, we gave away a penalty and the young kid (Holmes) missed, so we'll take it any way we can," Reds' Wallaby scrum-half Will Genia said.
"We had to win it and we spoke about coming out with plenty of energy and enthusiasm and we did that, so I'm very proud of the effort."
Fullback Luke Morahan scored the only try of an attritional Australian derby in the third minute with the remainder of the drab match decided by goalkicking.
Mike Harris kicked a conversion and two penalties for the Reds, while Holmes landed four penalties, but not his fifth and last attempt, which would have sealed victory.
Morahan enhanced his chances of selection as a Wallaby fullback with his dashing try after fielding a high kick deep in his own half and launching a counter-attack and scoring off his own kick ahead.
The Brumbies, who have been a revelation under the coaching of South African Jake White this season, gave themselves a hope of stealing the points with Holmes's last-ditch penalty kick after Saia Faingaa was penalised in a maul.
"I was really happy with the way we stuck at it," Brumbies captain Ben Mowen said, refusing to blame Holmes.
"We had a scrum five metres out from our try-line and we described how we would get up the field and give ourselves a chance to win it, and we did that, but it was a difficult kick.
"Sometimes they go your way and sometimes they don't."
Quade Cooper completed a full 80 minutes for the Reds for the first time this season, giving himself a chance of being selected in an extended Wallabies' squad for the June Tests after recovering from his serious knee injury at last year's World Cup.
Final Score Brumbies 12 (6) Reds 13 (10).
Pen - Z. Holmes 4
Tries - L. Morahan
Pen - M. Harris 2
Con - M. Harris
Referee: Steve Walsh
Assistant Ref 1: Angus Gardner
Assistant Ref 2: Andrew Lees
TMO: George Ayoub
Replacements: 16. Anthony Hegarty, 17. Ruaidhri Murphy, 18. Leon Power, 19. Ita Vaea, 20. Ian Prior, 21. Robbie Coleman, 22. Tevita Kuridrani.
1. Greg Holmes, 2. Saia Faingaa, 3. James Slipper, 4. Rob Simmons, 5. James Horwill (c), 6. Beau Robinson, 7. Liam Gill, 8. Scott Higginbotham, 9. Will Genia, 10. Quade Cooper, 11. Digby Ioane, 12. Mike Harris, 13. Anthony Faingaa, 14. Dom Shipperley, 15. Luke Morahan.
Replacements: 16. James Hanson, 17. Ben Daley, 18. Adam Wallace-Harrison, 19. Jake Schatz, 20. Nick Frisby, 21. Dallan Murphy, 22. Chris F'Sautia.