The visitors enjoyed the best of the early exchanges of the opening half, Felipe Contepomi wide with a 2nd minute drop goal attempt and the Argentines stopped inches short of the line after a seriers of rolling mauls.
Gordon D'Arcy lifted the siege with a superb break, his kick ahead finding touch in the visitor's 22 and when the Pumas infringed Sexton landed the kick.
With Brian O'Driscoll running the decoy line, Tommy Bowe and Jamie Heaslip combined to send Stephen Ferris over for a clinically worked 19th minute try that Sexton converted and minutes later Contepomi missed the opportunity to get his side on the board when he was wide with a relatively easy kick.
Sexton extended the lead with a 28th minute penalty as the Pumas went offside and three minutes later Contepomi finally opened Argentina's account with a penalty from the 22.
Indiscipline had by now crept into the Argentine game and tug on Stringer's jersey by Rodrigo Roncero allowed Sexton another free shot at goal that he didn't waste.
Contepomi continued his abysmal kicking with a missed 37th minute penalty and in injury time another cheap penalty allowed Sexton put sixteen points between the sides at half time.
Once again the former Leinster man was wide of the mark with a 47th minute penalty, made amends somewhat when on the mark in the 57th minute as Argentina enjoyed their best extended period of the game. However, as was the case throughout, all the marginal decisions went in favour of the home side and when they won a penalty at a scrum on the half way, it was indicitive of the Irish mindset that they opted for the kick at goals with Sexton once again on the mark.
Right at the death, O'Gara put through one of his trademark kicks that Keith Earls looked to have grounded but somehow the TV adjudicator decided it was not a try.
Ireland: Geordan Murphy, Tommy Bowe Brian O'Driscoll (c) (Keith Earls 69 min), Gordon D'Arcy, Andrew Trimble, Jonathan Sexton (Ronan O'Gara 69 min), Peter Stringer (Eoin Reddan 75 min); Cian Healy. Sean Cronin (Damien Varley 65 min),Tony Buckley (Tom Court 64 min); Donncha O'Callaghan, Mick O'Driscoll (Devin Toner 72 min); Stephen Ferris (Denis Leamy 61 min), David Wallace, Jamie Heaslip.
Argentina: 15 Martin Rodriguez, 14 Horacio Agulla, 13 Gonzalo Tiesi, 12 Marcelo Bosch, 11 Lucas Gonzalez Amorosino, 10 Felipe Contepomi (c), 9 Nicolas Vergallo, 8 Juan Fernandez Lobbe, 7 Julio Farias Cabello, 6 Genaro Fessia, 5 Patricio Albacete, 4 Mariano Galarza, 3 Martin Scelzo, 2 Mario Ledesma, 1 Rodrigo Roncero.Replacements: 16 Agustin Creevy, 17 Marcos Ayerza, 18 Juan Figallo, 19 Santiago Guzman, 20 Alvaro Galindo, 21 Alfredo Lalanne, 22 Lucas Borges.