The Ospreys had to overturn a half-time before Dan Biggar landing a last-minute penalty to snatch a 29-all draw with defending Pro12 champions Leinster at the RDS on Saturday.
It was the Irish province that had the better of the first half as Richardt Strauss and Dave Kearney went over. Jimmy Gopperth also added a drop-goal and a penalty, while Biggar responded for the visitors with nine points of his own as the hosts led 16-9 at the break.
The Ospreys came back in the early stages of the second half as tries from Joe Bearman and Ashley Beck gave them a 26-19 advantage.
However, Jack McGrath's touchdown and Gopperth's three-pointer appeared to have snatched the win, only for Biggar to have the last say.
The Welsh region suffered last season from recording three successive defeats to start the campaign, which saw them miss out on the play-offs. An opening day victory over Italian side Treviso was therefore a welcome result, but they faced a daunting task in going to the three-time Heineken Cup champions.
That was proven in the first 13 minutes as the host scored two tries and took a 10-3 lead. Despite Biggar converting a penalty opportunity early on, Leinster took command and Strauss went over after good work from Kearney. The full-back was then rewarded for his endeavour for the first score when he touched down.
Gopperth failed to convert both, but the fly-half added a drop-goal soon after.
After the respective fly-halves had traded penalties, the visiting pivot converted his third from the tee late in the half to reduce the arrears to 16-9 at the interval.
If Matt O'Connor's men had been in control in the first period, the second proved to be a different matter. Gopperth and Biggar were once again on target with the boot to take the score to 19-12, but an inspired passage of play quickly saw the Ospreys take the lead.
With 53 minutes on the clock, Bearman went over before Beck touched down soon after to give the Welsh side a seven-point advantage.
Sean Cronin was then controversially sin-binned for a series of collapsed scrums, but that perceived injustice only served to inspire the hosts as McGrath powered across the whitewash for a converted score.
Gopperth took Leinster ahead with a three-pointer but, with the final kick of the match, Biggar dramatically equalised.
Tries: Strauss, Kearney, McGrath
Pens: Gopperth 3
Drop goal: Gopperth
Yellow card: Cronin
Tries: Bearman, Beck
Con: Biggar 2
Pens: Biggar 5
Leinster: 15 Dave Kearney, 14 Darragh Fanning, 13 Brendan Macken, 12 Gordon D'Arcy, 11 Luke Fitzgerald, 10 Jimmy Gopperth, 9 Eoin Reddan, 8 Jordi Murphy, 7 Shane Jennings (c), 6 Kevin McLaughlin, 5 Mike McCarthy, 4 Devin Toner, 3 Mike Ross, 2 Richardt Strauss, 1 Jack McGrath.
Replacements: 16 Sean Cronin, 17 Jack O'Connell, 18 Martin Moore, 19 Tom Denton, 20 Rhys Ruddock, 21 Isaac Boss, 22 Ian Madigan, 23 Darren Hudson.
Ospreys: 15 Richard Fussell, 14 Ben John, 13 Andrew Bishop, 12 Ashley Beck, 11 Eli Walker, 10 Dan Biggar, 9 Tito Tebaldi, 8 Joe Bearman, 7 Sam Lewis, 6 Tom Smith (c), 5 James Kingm, 4 Ian Evans, 3 Joe Rees, 2 Scott Baldwin, 1 Ryan Bevington.
Replacements: 16 Richard Hibbard, 17 Duncan Jones, 18 Adam Jones, 19 Tyler Ardron, 20 Morgan Allen, 21 Tom Grabham, 22 Matthew Morgan, 23 Jeff Hassler.
Venue: RDS Dublin
Referee: Leighton Hodges (WRU)