The 30-year-old Munster winger has been fast-tracked into a Test squad missing Ireland's entire first-choice starting line-up and O'Sullivan insists he is there on merit.
He said: "Brian has done well for Munster since his arrival and has earned a call into the squad.
"He has moved across from league without too much disruption to his game and I thought this was a good time to move him onto the next level and see how he performs."
A casualty of Carney's elevation to the Test squad is Luke Fitzgerald, the gifted 19-year-old Leinster winger who made his debut in the autumn.
As expected, O'Sullivan has decided to rest his established senior players for the two-Test series in May and June.
Only Mick O'Driscoll is present from the side that thumped Italy 51-24 in the final RBS 6 Nations match last month when the Munster lock was a replacement for injured provincial colleague Paul O'Connell.
Ulster prop Simon Best will lead the squad against opponents who Ireland will also meet in the pool stages of the World Cup in September.
Seven uncapped players feature in the touring party, with Peter Bracken, Tony Buckley, Shane Jennings, Robert Kearney, Barry Murphy, Tomas O'Leary and Carney yet to make their Test debuts.
O'Sullivan has opted to select most of the substitutes bench used in the Six Nations, with the likes of Jerry Flannery, Isaac Boss, Neil Best and Andrew Trimble present.
Leinster lock Malcolm O'Kelly, Ireland's most capped player, will face the Pumas after missing the entire Six Nations with a knee injury.
O'Sullivan added: "This tour was always about looking at options with the World Cup in mind.
"It's an opportunity for players to put their cases forward for France and in doing so allow us to rest the majority of the Six Nations squad.
"Argentina is always a tough place to tour and this time will be no different.
"It gives us the chance to look at players in a pressurised Test match environment and, as well as some experienced players, there are also some new prospects there who will benefit from the experience."
The squad will gather on May 13 following the final round of Magners League matches and will depart for Buenos Aires seven days later.
Ireland will travel to Sante Fe City for the first Test on May 26 with the second staged in Buenos Aires on June 2.