Two goals from Lionel Messi helped cancel out earlier goals from Gamiero and Dani Parejo, as Barcelona dropped two points to Valencia at the Camp Nou.
But Marc-Andre Ter Stegen was left helpless when Gamiero struck the opener past him after Messi was dispossessed, and a counter attack ensued with Rodrigo putting Gamiero through.
Barcelona, who were earlier denied a penalty, saw one given against them when Sergi Roberto brought down Daniel Wass in the box.
Valencia went 2 goals up — looking to be running away with the game as Parejo converted the spot kick in the 32nd minute.
Seven minutes later, Barça were awarded with their own penalty, after Nelson Semedo was softly brought down in the area.
Messi, who seemed to have picked up a knock late in the game, got his second of the match and Barça’s equalizer in the 64th minute.
Vidal flicked a loose ball to the Argentine, who put a perfect curler past Valencia’s GK, Neto, from 20 yards out.
An entertaining night it was in a decently parked Camp Nou, as honours were shared by the two great sides.
The draw ensured that the Laliga title race remained open.