The Lions ended a 16 year losing streak in Canberra with a 20-29 bonus point victory over the Brumbies on Saturday.
The result is the Lions second victory this season and the Brumbies ninth loss of the season.
The Lions have now won two games in their last 25 matches and are still the bottom placed team in the Super Rugby standings.
Fly half Elton Janties played one of his best games in Super rugby and converted all four of the Lions tries and had a hand in three of the Lions tries.
Jantjies also kicked a penalty for the winners, while Stephen Moore and Andrew Smith had tries for the Brumbies.
Alwyn Hollenbach, Michael Rhodes, Jaco Taute and JC van Rensburg scored tries for the Lions.
The match was meant to be a celebration match for Matt Giteau was playing in his 100th Super Rugby game.
The Johannesburg-based Lions ended a run of seven defeats as they emphatically hit back from last week's 53-19 pasting by the Cheetahs to ambush the two-time Super champions on their own ground.
Former All Black coach John Mitchell was rewarded after his drastic overhaul of the Lions' team, making 10 changes from the side crushed by the Cheetahs.
Despite having the second-worst defence in the southern hemisphere provincial championship, the Lions defended stoutly against the Brumbies and fought back from 10-0 down after the opening 17 minutes.
It was 20-year-old flyhalf Jantjies, the South African young player of 2010, who sparked the revival setting up tries for centre Alwyn Hollenbach and fullback Jaco Taute with brilliant passes.
Jantjies, who kicked three conversions and a penalty, jinked through the defensive line and popped an instinctive 'no-look' pass for Taute's match-sealing bonus point try with 20 minutes left.
"We're ecstatic. We've worked really hard this week and we really wanted this one tonight," skipper Josh Strauss said.
"We've been talking about it all season and finally it came through for us tonight."
The home side started the match strongly, with hooker Moore's try to the right of the posts in the 10th minute, following several phases, after flanker Colby Faingaa made a 30-meter break.
Giteau converted and put the side a further three points ahead to 10-0 when Lions prop Patric Cilliers was sinbinned for dumping Brumbies scrumhalf Josh Valentine in the 18th minute.
Despite being a man down, the Lions began to keep the ball over several phases at the Brumbies line and it yielded a try for flanker Michael Rhodes.
Lions five-eighth Elton Jantjies converted to reduce the score to 10-7, and the visitors continued to keep possession and territory as the half progressed.
Six minutes before halftime, the Lions went 12-10 ahead, after several phases bashing at the Brumbies line, before three passes left created an overlap for winger Van Rensburg to score untouched.
After leading 10-12 at half time the Lions played the second half with greater intensity and only allowed the Brumbies to score a consolation try 5 minutes from time.
It was a bitter 100th Super rugby appearance for Brumbies' skipper Matt Giteau, who could not disguise his disappointment.
"We gave away penalties, the game went slow and we let them back into it and for whatever reason it just seemed like we were pretty flat, I don't know what can you say," said Brumbies captain Matt Giteau, who was playing his 100th Super rugby game.
"We lost a lot of ball at the breakdown and everyone was looking for tries and we got away from the simple stuff we were doing well...and we just slipped away."
Final Score Brumbies 20 Lions 29
Tries - S Moore,A. Smith
Pen - M Giteau 2
Con - M Giteau 2
Tries - M Rhodes, JC Janse van Rensburg, A.Hollenbach, J Taute
Pen - E Jantjies
Con - E Jantjies 4
Cards - Patric Cilliers (17) Yellow
Referee: Nathan Pearce (Australia)
Assistant referees: James Leckie (Australia), Andrew Lees (Australia)
Television match official: Matt Goddard (Australia)
Brumbies:1. Ben Alexander , 2. Stephen Moore , 3. Salesi Ma 'afu , 4. Peter Kimlin , 5. Ben Hand , 6. Mitch Chapman , 7. Colby Faingaa , 8. Ita Vaea , 9. Josh Valentine , 10. Matt Giteau , 11. Adam Ashley-Cooper , 12. Christian Lealiifano , 13. Tyrone Smith , 14. Andrew Smith , 15. Pat McCabe
Replacements , 16. Huia Edmonds , 17. Jono Owen , 18. Mark Chisholm , 19. Michael Hooper , 20. Patrick Phibbs , 21. Robbie Coleman , 22. Henry Speight
Lions :Jaco Taute, Lionel Mapoe, Dylan Des Fountain, Alwyn Hollenbach, Deon van Rensburg, Elton Jantjies, Jano Vermaak, Josh Strauss (capt.), Michael Rhodes, Derick Minnie, Franco van der Merwe, Wikus van Heerden, Patric Cilliers, Bandise Maku, JC Janse van Rensburg.
Replacements: Edgar Marutlulle, Kevin Buys, Warren Whiteley, Cobus Grobbelaar, Rory Kockott, Burton Francis, Butch James