A last-minute try from Isa Nacewa saw the Barbarians edge Wales 31-28 in a nine-try thriller at the Millennium Stadium in Cardiff on Saturday.
The result is the Baa-baas' second success in as many weeks after getting the better of England last week.
Wales meanwhile were left to reflect on a poor overall performance that will leave coach Warren Gatland with more questions than answers in the build-up to the World Cup.
The Barbarians dominated the first half, largely thanks to their superiority in the set pieces, and deservedly lead 19-14 at the break. The hosts came back strongly in the second period to regain the lead but they failed to close the game out as two tries in the last ten minutes allowed the Barbarians to snatch victory.
Wales took the early lead when wing George North took a pass from Gavin Henson to score the opening try but the Barbarians hit back to lead at the break as Iosefa Tekori, Nacewa and captain Sergio Parisse crossed, with Morgan Stoddart getting Wales' second try.
Wales moved back in front in the second period thanks to Mike Phillips and Aled Brew with Stephen Jones adding the conversions on his 100th cap, but Mathieu Bastareaud got a try back for the Barbarians before Nacewa profited from a superb Willie Mason pass to sprint almost the full length of the field to snatch victory in the last move of the match.
Tries: North, Stoddart, Phillips, Brew
Cons: Jones 4
Tries: Tekori, Nacewa 2, Parisse, Bastareaud
Cons: James 3
Yellow cards: Brew (Wales - 44th min);
Wales: 15 Morgan Stoddart, 14 George North, 13 Jonathan Davies, 12 Gavin Henson, 11 Aled Brew, 10 Stephen Jones, 9 Mike Phillips, 8 Toby Faletau, 7 Sam Warburton (capt), 6 Dan Lydiate, 5 Luke Charteris, 4 Ryan Jones, 3 Paul James, 2 Huw Bennett, 1 Nathan Bevington.
Replacements: 16 Lloyd Burns, 17 Scott Andrews, 18 Alun-Wyn Jones, 19 Josh Turnbull, 20 Tavis Knoyle, 21 Rhys Priestland, 22 Nathan Williams.
Barbarians: 15 Isa Nacewa, 14 Paul Sackey, 13 Seru Rabeni, 12 Mathieu Bastareaud, 11 Doug Howlett, 10 Brock James, 9 Sebastien Tillous-Borde, 8 Sergio Parisse (capt), 7 Martyn Williams, 6 Joe van Niekerk, 5 Paul Tito, 4 Iosefa Tekori, 3 Carl Hayman, 2 Sebastien Bruno, 1 Iestyn Thomas.
Replacements: 16 Leonardo Ghiraldini, 17 Davit Kubriashvili, 18 Erik Lund, 19 George Smith, 20 Lloyd Williams, 21 Willie Mason, 22 Benoit Baby.
Venue: Millennium Stadium, Cardiff
Referee: Alain Rolland (Ireland)
Assistant referees: Peter Fitzgibbon (Ireland), Simon McDowell (Ireland)
Television match official: Graham Hughes (England)