The young fly half spilled the ball as he tried to run from defence in the closing minutes, allowing Felipe Contepomi to kick what looked like a match winning penalty for Leinster.
However with the clock ticking down the Ospreys worked into an attacking position and were awarded a penalty 45 metres out which Jones knocked over to ensure the champions started with a win.
However the Ospreys should had a more comfortable victory outscoring Leinster three tries to one – but were let down by a series of errors which allowed the boot of Contepomi to keep the Irish side in the game.
Andrew Bishop claimed two touchdowns and Barry Williams notched
one, while Rob Kearney scored the only Leinster try to add to Contepomi’s five penalties.
The Ospreys led by only five points at the break despite having far the better of the first half. They made a dream start when youngster Andrew Bishop crossed with just 20 seconds on the clock.
The 20-year-old charged down an attempted clearance from Leinster wing Rob Kearney and had the pace to claim the touch down. Contepomi replied with a penalty but the Ospreys moved up a couple of gears to claim their second try.
Skipper Barry Williams did the damage, charging over from short range after good line-out work from Andy Lloyd. But Contepomi cut the deficit in first-half injury-time when he fired over two penalties in rapid succession.
Contepomi added his fourth penalty early in the second half and the Ospreys found it hard to respond. Eventually Bishop went over for his second try, set up by Leigh Davies and Jason Spice, before Girvan Dempsey created Kearney’s score.
Leinster appeared to have won with Contepomi’s fifth strike, but Jones had the final say.