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.
The sexual habits of the former French presidential hopeful were at the centre of trial 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.
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.
Passing through the brutalist architecture of Lille’s courthouse this morning came the colourful parade of characters whose private behaviour has been pored over by the world’s media. Having been subject to moral judgements for months now, they came to hear the legal ones.
In the courtroom, DSK sat, largely immobile, in a dark suit and tie, hands folded in his lap as the defendants walked one by one to the stand to hear their verdict.
When his time came, he stood stiffly at the stand, looking straight ahead as the charges were read aloud.
The man who had one day hoped to be president of France showed almost no response when his acquittal came.
Entering the courthouse before the verdict, Dodo said the trial “was meant to topple DSK”. If it was, it didn’t work. And today Dominique Strauss-Khan walked free.
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.
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.