The fly-half played in all three Tests against the Qantas Wallabies before moving to Racing Metro to play in France's domestic league.
Sexton admits he had discussions with Ireland head coach Joe Schmidt, regarding his fitness, before confirming his availability for the two-Test tour against Los Pumas - which starts on Saturday at Estadio Centenario.
And the 28-year-old says he is feeling very fresh and he never considered not travelling with the touring party.
"I'm fresher than I have been in years gone by on summer tours. I suppose that's not always a good thing, because it means you have not played as many knock-out games as you would have liked.
"Since Christmas I had a week off because we had a week off before our (Racing Metro's) European Cup campaign was over so I got away then."