Turning Point: Spain led 55-49 with 10 minutes to go but were held to just one basket in the final quarter as Turkey went on a 16-2 run en route to victory.
Game Hero: Turkey's Ersan Ilyasova had a game-high 11 boards to go with his six points.
Stats Don't Lie: Turkey outrebounded Spain 37-33.
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Turkey upset Spain 65-57 in Group A of the EuroBasket on Monday to claim two valuable points in the standings in Round 2.
Orhun Ene's side, which got 18 points from Emir Preldzic, could not have asked for a better day because early on the day, Turkey didn't know if they would even advance.
But Great Britain defeated Poland, who had upset Turkey on Sunday, to ensure the Turks played in the next phase of the competition.
Spain didn't have their biggest weapon, with Pau Gasol missing the game because of a sprained ankle suffered in their blowout of Lithuania on Sunday.
The setback was the first in the tournament for Spain.
"It was an amazing feeling in the changing room when Great Britain beat Poland," said Turkey's Ersan Ilyasova, who had a game-high 11 boards to go with his six points.
"This victory against Spain is a huge boost in confidence for us ahead of Round Two."
Spain led 48-40 midway through the third quarter but went into the final frame up 55-49.
Felipe Reyes' jumper then gave Spain a 57-49 advantage with less than nine minutes to go only for he and his team-mates to miss the remainder of their shots with Turkey reeling off 16 unanswered points.
Big man Omer Asik and Hedo Turkoglu each had 12 points for Turkey, with Endar Arslan scoring 10 and handin out six assists.
In defeat, Spain's Marc Gasol had 12 points and both Rudy Fernandez and Reyes contributed 11.
Serge Ibaka also weighed in with nine points and a team-high eight rebounds.