Leinster fell behind to unconverted tries from hooker Benjamin Noirot in the 6th minute and then by right wing Philippe Bidabé three minutes later in what was a blistering start to the season in the heat of the south of France.
But moments later back-row forward Sean O'Brien capped off some fine inter-play involving Gary Brown and Chris Whitaker to touch down, with out-half Jonathan Sexton converting to leave the score 10-7 after 12 minutes.
The pendulum swung in the hosts' favour once more when flanker Agustin Creevy broke to dive over the line, with France international Dimitri Yachvili adding the points.
Leinster silenced the vociferous home crowd of over 9,000 thanks to a breakaway Rob Kearney try after he fielded a kick inside his own 22.
The 21-year-old Ireland international showed great awareness to sprint clear and touch down under the posts. Sexton added the points to leave the Blues trailing 17-14 as the game approached the half hour mark.
Leinster squeezed and pressed and capped off a massive drive from the pack and a swift shift across the backline that found impressive centre Michael Berne inside the Biarritz 22 who crashed over, with Sexton again slotting home the conversion.
Yachvili added a penalty on the stroke of half-time for the hosts to reduce the deficit to one point, leaving the score 21-20 at the interval.
The visitors made a raft of replacements at the interval but it was Biarritz who regained the initiative with a 47th minute penalty from substitute Julien Dupuy, and he added another three-pointer after 68 minutes.
The French side added their fourth try of the evening seven minutes later through sub hooker Matias Cortese and although substitute Christian Warner converted his own try in the last minute, Leinster fell to a narrow three-point defeat.
Leinster and Biarritz have faced each other on five occasions in the Heineken Cup, with the Irish side claiming thee victories.