The man of German and Russian origin was arrested during a police operation near the town of Tuebingen in the south-western state of Baden-Wuerttemberg.
The suspect had been hoping to trigger a drop in the football club's share price, prosecutors said.
According to the investigation, the man had bought 78,000 euros ($A111,000) worth of shares in the club online from the team's hotel, where he had been staying since April 9.
Three blasts went off as the team bus left the hotel on its way to a game on April 11, leaving two injured. Dortmund defender Marc Bartra suffered a right wrist fracture and injuries from shards of glass from the explosion.
The scheduled match against AS Monaco was postponed as a result of the explosions.
The incident initially was treated as a terrorist incident after a note hinting at an Islamist connection was found at the scene.
Police said the explosive devices were placed in a hedge near the hotel's car park.