Even though Arwel Thomas emerged with a 100 per cent kicking record for 19 points, the home team outscored the tourists by three tries to two to make it five wins over major touring teams in the Nineties.
Wales now face a long haul up country to face Tucuman on Tuesday and must improve before the first Test against the Pumas on Saturday.
"Now we know what to expect from Argentina. BA played very well and they stopped us from gaining any continuity in our game," said the Wales tour manager, David Pickering. "We could have played better, but there were a lot of offsides and not enough momentum in our game. This was our first outing and six or seven of the players were new to this level."
Having beaten France twice, South Africa and England in the nineties, Nicolas Miranda's BA were quietly confident of taking another scalp. They had to battle long and hard to earn it, however, with those tries from wings Octavio Bartolucci and Tomas Solari proving vital in the third quarter.
For their part, the Welsh team produced the try of the game on the stroke of half-time when the centre Leigh Davies raced 45 metres to round off a move that had started in his own 22.
Buenos Aires: D Albanese; O Bartolucci, E Simone, J Orengo, T Solari; J Cilley, N F Miranda, capt; F Guatieri, M Ledesma, F Alberdi, I Lobbe, P Sporleder, R Martin, L Ostiglia, P Camerlinckx.
Wales: S Howarth; G Thomas, A Bateman, L Davies, D James; A Thomas, R Howley, capt; P Rogers, G Jenkins, X Anthony, M Voyle, C Wyatt, C Charvis, B Sinkinson, G Lewis.
Referee: C White (England).Reuse content