In a poor spectacle at Bayonne’s Stade Jean-Dauger, both sides missed a succession of kicks while the hosts’ handling was terrible throughout.
Two successful penalties from South African Jacques-Louis Potgieter put the hosts 6-0 up, but he also missed a trio of kicks.
Biarritz's France scrum-half Dimitri Yachvili converted one of his own just before the break, missing a penalty and a drop goal before levelling on the hour mark.
But the last laugh should have been with the hosts as Cedric Garcia, who had just come off the bench, missed a 73rd-minute penalty he had won, his side’s fourth failure of the night.
The result leaves Bayonne 11th in the standings, 10 points clear of Agen in 12th, while Biarritz are six points above their rivals in ninth.