Border Reivers had to survive a late two-try rally by the Blues to edge the Celtic League spoils at Netherdale.
Borders: (16) 26:
Tries: McGee, Walker
Cons: Hore 2
Pen: Hore 4
Cardiff Blues: (3) 23:
Tries: Stcherbina, Molitika
Cons: Macleod 2
Pens: Macleod 3
Tom McGee grabbed the home side's first try after a blunder from Jonah Lomu and the kicking of Charlie Hore built up a 16-3 lead at the interval.
Nikki Walker crossed the line to extend the Borders' advantage before the visitors set up a thrilling finish.
Centre Marc Stcherbina touched down and Craig Quinnell grabbed another try but the Borders held on to win.
Both teams struggled to settle in spite of the ideal conditions, preferring to kick away possession rather than attempt to build handling moves.
But the Borders quickly rattled up 10 points in a quickfire sequence.
Hore broke the deadlock with a confidently-struck penalty; then prop McGee bagged a sizzling try straight from the restart.
Lomu spilled the ball under no pressure, allowing the Reivers to sweep up field with hooker Ross Ford involved three times.
Lock Scott MacLeod could have reached the line himself but unselfishly unloaded to McGee, who was left with a stroll, and Hore added the extras.
The Blues hit back with a simple penalty by Nicky Macleod but Hore replied in identical fashion to restore the advantage.
Reivers winger Simon Danielli then let the ball slip from his grasp just a couple of paces short of the try-line.
Hore completed his penalty hat-trick to give his side a useful 13-point cushion at the break.
The rattled Blues came out with more urgency after the restart and Macleod added two penalties.
The visitors set up camp in the 22-zone but found the Borders defence in mean mood and could not make the breakthrough.
Having weathered the storm, the Reivers created a fine second touchdown.
Danielli came into the line in midfield to provide the time and space for Stuart Moffat to send Walker over.
Hore again converted - then banged over another penalty.
The Blues refused to buckle, however, and an opportunist try by Stcherbina - converted by Macleod - ensured a tense finale.
There was more drama in stoppage time when Quinnell grabbed another touchdown, also converted by Macleod.
Blues coach Dai Young:
"We had enough possession to win it five times, but lacked a cutting edge.
"Credit to the Borders, their defence was very disciplined throughout."
Borders: MacRae, Danielli, MacDougall, Law, Walker, Hore, Cusiter, McGee, Ford, Douglas, MacLeod, Palepoi, Brown, Sititi, Miller.
Replacements: Moffat for MacRae (23), Parr for McGee (60), Scott for Ford (71), Stewart for Palepoi (71), Dalziel for Miller (55). Not Used: Rennick, McKearchar.
Blues: Morgan, Czekaj, Stcherbina, Davies, Lomu, Macleod, R. Powell, Yapp, Goodfield, B. Evans, D. Jones, Goode, Molitika, Schubert, Sowden-Taylor.
Replacements: Dewdney for Czekaj (61), L. Thomas for Davies (69), W. Evans for R. Powell (75), Quinnell for D. Jones (69), Lewis for Schubert (69). Not Used: R. Thomas, M. Jones.
Referee: Alain Rolland (IRFU).