
Dominique Strauss-Kahn had admitted to attending sex parties
Mr Strauss-Kahn stood alongside 13 co-defendants, most of whom were also acquitted of "aggravated pimping".
He has always denied knowing that some of the women who took part in orgies he attended were prostitutes.
Lurid details of the former French presidential hopeful's sex life emerged at hearings in Lille in February.
Although using prostitutes is not illegal in France, assisting in supplying them is illegal and regarded as procuring. Mr Strauss-Kahn had been accused of playing a pivotal role in facilitating the orgies.
The verdict brings to a close four years of legal proceedings against Mr Strauss-Kahn, including charges of attempted rape which were later dropped in 2012.
Mr Strauss-Kahn gave little reaction while the verdict was being read out, but he was overheard saying to his daughter afterwards: "All that for this? What a waste".
His lawyer, Henri Leclerc, told journalists: "Everyone can see there was no legal basis in the case and all the noise that has surrounded this story has given us all something to think about."
The chief judge said Mr Strauss-Kahn behaved as a client and had not paid the sex workers he met. He only benefitted from others paying them to be present for group parties, the judge added.
Among the others acquitted was Belgian brothel owner Dominique Alderweireld, also known as Dodo la Saumure, who was accused of supplying prostitutes for the parties.
Recreational sessions
The former public relations chief of Hotel Carlton in Lille, where some of the sex parties took place, was the only defendant found guilty.
Rene Kojfer was given a year's suspended sentence for his involvement in recruiting prostitutes and was fined €2,500 (£1,800).
Dominique Strauss-Khan would have faced a 10-year jail term if found guilty.
During the three weeks of hearings in February, sex workers described Mr Strauss-Kahn's rough behaviour at some of the parties. But he argued that he was not on trial for "deviant practices".
He told the court he participated in the parties because he needed "recreational sessions" amid one of the world's worst financial crises.
Friday's verdict was not a surprise as the state prosecutor Frederic Fevre had recommended Mr Strauss Kahn's acquittal, saying there was not enough evidence to back up the pimping charge. However, Mr Fevre had asked for his co-defendants to be convicted.
Five of the six plaintiffs - including four prostitutes - had also dropped their accusations against the 66-year-old because of a lack of evidence.
While Mr Strauss-Kahn has admitted to being present at the orgies, he has always maintained that he did not know that some of the women involved were being paid.
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French media reaction
Several French commentators are unsurprised by the verdict and question whether the case should have come to trial at all.
"This shipwreck of an investigation had already been heralded by the prosecutor Frederic Fevre who... recommended several acquittals... noting that judges work 'with the penal code and not with the moral code'" - Pascale Robert-Diard's "Chroniques judiciaires" blog in Le Monde
"The unbridled libido of the key player may be a physiological peculiarity, but it falls more within the sphere of a medical publication than in works issued by Dalloz [French publisher specialising in legal reference books]" - Le Figaro