The Ospreys stumbled into the Magners League play-offs as they came from behind to win at Aironi.
The Welsh side's cause was not helped by the erratic Dan Biggar, the fly-half missing four of seven penalties.
The Italian side have won one game in the league this season but led 7-3 at half-time thanks to Danwel Demas' try.
But a late James Hook penalty, coupled with the Scarlets' win over Cardiff Blues back in Wales, was just enough to book a trip to Munster next Saturday.
Ospreys coach Sean Holley was pleased to have secured a play-off berth but admitted they had done it the hard way.
"We're disappointed with our display, we're disappointed with our form since the Six Nations," Holley said.
"But you have to say the introduction of the play-offs, over the course of 22 games... the table doesn't lie and in that respect we just about deserve to be in there for our efforts throughout the season.
"We're delighted to be there but just a little bit disappointed with how we've played recently.
"I think we played most of the rugby tonight, I think we went out to try and win it, not to not lose it.
"We missed some crucial kicks at goal and a drop-goal and showed a little bit of impatience at times in our attack, we lost the ball a hell of a lot.
"But full credit goes to Aironi, they defended really well, they tackled hard and they made it extremely difficult for us to win.
"We've got to go to Thomond Park now, it's the fifth time we've played Munster [this season] and it'll be a cracking Saturday night.
"For us the shackles are off, we felt a little bit of pressure - we admit that - in the last couple of weeks... but now our season restarts."
Aironi: Horacio San Martin; Matteo Pratichetti, Gilberto Pavan, Gabriel Pizarro, Danwel Demas; James Marshall, Tito Tebaldi; Alberto de Marchi, Luigi Ferraro, Fabio Staibano, Marco Bortolami, Quintin Geldenhuys, Joshua Furno, Josh Sole, Gareth Krause
Replacements: Fabio Ongaro for Ferraro (41), Andrea de Marchi for Alberto De Marchi (76), Luca Redolfini for Staibano (71), George Fabio Biagi for Bortolami (78), Nicola Cattina for Krause (43), Pablo Canavosio for Tebaldi (72), Giulio Toniolatti, Riccardo Bocchino.
Ospreys: Richard Fussell; Tommy Bowe, Andrew Bishop, James Hook, Nikki Walker; Dan Biggar, Rhys Webb; Paul James, Richard Hibbard, Adam Jones, Ryan Jones, Alun Wyn Jones (capt), Justin Tipuric, Marty Holah, Jonathan Thomas.
Replacements: Huw Bennett, Ryan Bevington for James (49), Duncan Jones, Ian Gough for Holah (59), Tom Isaac for Biggar (60), Tom Smith for Tipuric (74), Ashley Beck for Bishop (48), Sonny Parker for Webb (70).
Referee: Andy MacPherson (SRFU).