Ireland required a late drop goal from Ronan O'Gara to avoid a first defeat by Italy in the RBS 6 Nations.
The Azzurri crept 11-10 ahead in the 76th minute through a try from Luke McLean and one of the championship's greatest upsets looked likely.
But Ireland, who started as overwhelming 1/8 favourites, hit back two minutes later when O'Gara was on target from in front of the posts.
It was dismal start to the campaign for a side hoping to be in the title mix, but there was nothing on show at the Stadio Flaminio today to suggest they can win the Six Nations.
Brian O'Driscoll crossed in the 44th minute while Jonathan Sexton kicked five points, but it was otherwise a torrid afternoon for the 2009 champions.
They dazzled with some thrilling running but time and again failed to capitalise, making desperately hard work of subduing stubborn but limited opposition.
Worryingly for Ireland, they are group rivals at this year's World Cup and the teams are due to meet on October 2. Italy will only have been encouraged by today's events.
The lack of composure at crucial moments will concern head coach Declan Kidney with chances blown by handling errors from O'Driscoll, Gordon D'Arcy and Keith Earls.
Ireland were missing 12 Test players to injury, among them Jamie Heaslip and Tommy Bowe, yet still fielded a side averaging 35 caps per player.
Leinster winger Fergus McFadden was the only debutant but prop Mike Ross and number eight Sean O'Brien were making their first appearances in the championship.
It was an afternoon they will want to forget with Mirco Bergamasco kicking a penalty to give Italy first blood.
Unforced errors hampered Irish attempts to make inroads with O'Brien spilling the ball forward and O'Driscoll letting fly with a wild pass.
They exploded into life in the 20th minute with Earls and Luke Fitzgerald using quick ball to release Sexton, but the Leinster fly-half was caught five metres out.
Full-back McLean executed a try-saving tackle on O'Driscoll as Ireland renewed their assault.
Italy were buckling but were saved on two overlaps when first Earls juggled with the ball, conceding precious moments for the Azzurri to react, and then D'Arcy dropped a simple pass.
The one-way traffic continued but it took until the 27th minute for Ireland to level the score with a penalty from Sexton.
Bergamasco missed a long but straight three points amid a promising period from Italy, who saw hard-running centre Alberto Sgarbi make ground.
Pressure from their front row resulted in Ireland being penalised at a scrum and it was now visitors' turn to weather the storm.
Burton failed with a poorly-advised drop-goal - the Azzurri seemed to be moving nicely through the gears - before the half finished with Bergamasco landing his second penalty.
A powerful run from Denis Leamy signalled Ireland's intent for the second half and just three minutes in they raced ahead.
Earls carried the ball over the gainline and, once Sexton had returned from a blind ally, play was swept left where O'Driscoll ignored an overlap and scampered over from close range.
Sexton nailed a tricky conversion and then placed Ireland deep in Azzurri territory with a towering touchfinder.
Earls and O'Driscoll made inroads before the Ireland skipper launched another wild pass that sailed into touch with the line beckoning McFadden for an easy run in.
Italy were continuing to resist stubbornly, kept in the game by Irish errors at key moments as much as their own heroics with D'Arcy spilling the ball two metres out.
For all Ireland's pyrotechnics, they were still only 10-6 ahead and, when Italy's pack set off on a rolling maul that took them 10 metres short of the line, their position looked precarious.
The Azzurri were in their element as a series of scrum followed, before centre Gonzalo Canale was brought down on the crash with a shuddering hit.
Leamy was sin-binned for killing the ball and the drama continued when Italy continued to use their pack to batter the whitewash.
Sergio Parisse almost scampered through but they were not to be denied in the 76th minute when slick handling sent McLean in at the left corner.
Italy suffered the cruellest of blows with two minutes to go, however, when substitute O'Gara landed a drop goal to snatch victory.