Warren Gatland's men beat the 2007 World Cup semi-finalists 28-13 in Cardiff to finish their warm-up campaign with a flourish.
Andy Powell, Alun Wyn Jones and George North scored tries for the home side, with Argentina's only five-pointer coming through Martin Scelzo in the dying moments.
Lions tourist James Hook produced another assured display, this time at fly-half, scoring 13 points in a 100-per-cent showing with the boot.
The result sees Wales head to New Zealand in good spirits as they prepare to face reigning World Champions South Africa on September 11.
Things aren't looking so good for the Irish, however, who went down to a second successive defeat to France.
Beaten 10-6 by Scotland in their first friendly fixture at Murrayfield, Declan Kidney's side lost to the French in Bordeaux a week ago before suffering the same fate in Dublin on Saturday.
Ireland led 8-0 thanks to an early Cian Healy try and a Jonathan Sexton penalty but France scored 26 unanswered points to surge into an unassailable lead.
Sexton and O'Brien claimed consolation scores for the Irish but the result was yet another disappointing one for an Irish team who welcomed back Lions trio Brian O'Driscoll, Gordon D'Arcy and Stephen Ferris from injury.
Ireland now host England at the Aviva Stadium this Saturday as look to avoid a World Cup warm-up whitewash ahead of the tournament opener against the USA.