Leinster lost to the Border Reivers for the first time in three league meetings as out-half Steve Jones sent over the match-winning drop goal at Netherdale.
MAGNERS LEAGUE: Friday, October 13
BORDER REIVERS 22 LEINSTER 19, Netherdale (Att: 1,661)
Scorers: Borders: Try: Craig Hamilton; Con: Calum MacRae; Pens: MacRae 4; Drop: Steve Jones
Leinster: Try: Stephen Keogh; Con: Felipe Contepomi; Pens: Contepomi 4
Battling Borders broke their Magners League duck with a backs-to-the-wall display against Michael Cheika's Leinster side, who were gunning for their third win on the trot.
Despite a gutsy show, the Scots looked like being denied that elusive first win until Jones' late drop goal settled a rugged contest. Leinster took just two minutes to break the deadlock when Borders strayed offside and Felipe Contepomi slotted the penalty.
However, fears of a rout were quickly eased as Calum MacRae launched a thrilling counter attack from which the Reivers eventually took the lead. The full-back side-stepped two tackles before Scott Gray's grubber kick was brilliantly picked up by Craig Hamilton, who plunged over near the posts.
MacRae added the conversion before increasing the home side's lead with an easy penalty.
Borders belied their basement position as they continued to trouble the visitors but Leinster reduced the leeway when Ross Beattie's challenge on Guy Easterby was ruled illegal and Contepomi again bisected the posts.
The Reivers hit back with thrilling breaks from Kelly Brown and Chris Cusiter but they were denied a second try when Opeta Palepoi spilled a pass at the crucial moment. Instead, they had to be content with a second MacRae penalty before Leinster turned the screw ahead of the break.
First, former Munster flanker Stephen Keogh was driven over for a try, converted by Contepomi, before the Argentinian's injury-time penalty gave the visitors what was a flattering 16-13 half-time lead.
Contepomi appeared to have put Leinster in control against a tiring Reivers outfit with his fourth penalty soon after the restart. However, the Borders refused to buckle under the mounting pressure and instead launched another counter attack to put themselves firmly in contention for their first win over Leinster since January 2005.
MacRae reduced the deficit following another infringement by Leinster before Scotland scrum half Cusiter sprinted 40 metres to take his side within metres of a second try. But superb Leinster tackling kept them out and instead it took another MacRae penalty to level the scores.
Then, in a dramatic finale, Jones dribbled over the decisive drop goal before Borders withstood heavy injury-time pressure from Cheika's charges, who now lie in fifth position in the table.
Borders: Calum MacRae; Mark Robertson, Ben MacDougall, Garry Law, Nick De Luca; Steve Jones, Chris Cusiter (capt); Gavin Kerr, Ross Ford, Ed Kalman, Opeta Palepoi, Craig Hamilton, Ross Beattie, Scott Gray, Kelly Brown.
Replacements used: John Dalziel for Beattie (42 mins), Bruce Douglas for Kalman (60), Steve Scott for Ford (74), Andy Miller for Gray (75). Not used: Scott Newlands, Brendan McKerchar, Gregor Townsend.
Leinster: Rob Kearney; Luke Fitzgerald, Brian O'Driscoll (capt), Gordon D'Arcy, Denis Hickie; Felipe Contepomi, Guy Easterby; Reggie Corrigan, Brian Blaney, Will Green, Trevor Hogan, Malcolm O'Kelly, Cameron Jowitt, Keith Gleeson, Jamie Heaslip.
Replacements used: Cillian Willis for Easterby (21 mins), Stephen Keogh for Jowitt (26), Kieran Lewis for Hickie (48), Harry Vermaas for Corrigan (59), Owen Finegan for Hogan (65), Bernard Jackman for Jowitt (70). Not used: Christian Warner.
Referee: Neil Ballard (Wales)