The Ostankinsky District Court found Lebedev, who owns several major newspapers in Russia and Britain, guilty of assaulting construction magnate Sergei Polonsky in September 2011, Russian news agencies reported.
Lebedev, a maverick banker and former intelligence officer who owns Moscow's opposition newspaper Novaya Gazeta together with Mikhail Gorbachev, has labelled the case as fabricated.
Nearly two years ago, Lebedev appeared alongside flamboyant construction magnate Sergei Polonsky in a talk show on NTV channel. When an argument broke out, he got up and delivered several punches to Polonsky, who fell out of his chair.
Defence lawyer Genri Reznik vowed to appeal the verdict on today, telling journalists that the entire case was an effort to punish Lebedev for investing into Novaya Gazeta, a tri-weekly newspaper fiercely critical of the Kremlin.
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Under Russian law, "compulsory labour" is unpaid work that the convict must engage in outside his regular work, which benefits society and can be carried out not more than four hours per day.
Lebedev has also owned British papers The Evening Standard since 2009 and The Independent since 2010. His son Evgeny Lebedev, who is the chairman of publisher Independent Print Ltd, flew in for the court hearing, according to his Twitter blog.
However last week, prosecutors in the case asked the judge to drop the hooliganism charge, essentially ruling out a prison sentence.
The 53-year-old, who has complained of government pressure and last year said he will sell his Russian assets due to continuing persecution, dismissed the charges as a fabrication.
Polonsky, known for eccentricities, outrageous remarks and a lavish lifestyle, last week posted on his Facebook page a letter in which he asked the judge to find Lebedev not guilty.