Iyad Ag Ghali, a Tuareg separatist commander, was asked by Berlin to negotiate with Algerian kidnappers in 2003 for the release of 14 tourists seized in the Sahara, including nine Germans, later paying them a ransom of 5 million euros supplied by Germany, Spiegel added.
Ag Ghali was "our man", Spiegel quoted a former top German official as saying. The foreign ministry declined to comment.
France has deployed ground troops in Mali and its war planes have bombed rebel columns and bases, halting the Islamists' advance. The intervention aims to stop militants from tightening their grip on Mali's northern desert zone and using it as a springboard for attacks in Africa and on the West.
The region has been occupied by a mix of gunmen since rebels bolstered with weapons seized from Libya after the 2011 fall of Muammar Gaddafi took up arms last year.Separatist rebels who launched the fighting were soon sidelined by the Islamist alliance of al Qaeda's North African wing AQIM and home-grown Malian groups Ansar Dine and MUJWA.
Citing the German intelligence agency (BND), Spiegel said the Malian government had hoped it might negotiate with the Islamists through Ag Ghali, but efforts ended with the push south by rebels that led to French military intervention.
In Germany senior politicians including from the ruling coalition have criticized Foreign Minister Guido Westerwelle's response to the crisis as inadequate, reviving a long-running and sensitive debate about the role of Germany's armed forces.
Berlin immediately ruled out sending any combat troops as French forces began their mission, but sent two troop transport planes to West Africa and said Germany would join a European Union training force for Malian troops.
In a piece for Bild am Sonntag newspaper on Sunday, Westerwelle wrote that Germany was "engaging decisively in the fight against terrorism."