The court ruled that journalist Aleksandr Krutov should be paid 1,000 euros ($1,500) as compensation for moral damages in a defamation verdict that went against him and to cover court costs.
Krutov told RFE/RL that the court decision is a crucial precedent for journalists in Russia.
Krutov appealed to the Strasbourg court seeking the reversal of a verdict by a Russian court that he said violated his freedom of speech.
In January 2003, Krutov wrote an article in a local newspaper in which he stated that regional prosecutor Anatoly Bondar and his office were involved in a feud between elite groups in the western Russian city of Saratov and were receiving bribes in the process.
Bondar sued Krutov for defamation and won the case.
Krutov has been fighting in Russia to have the court's original decision overturned.
Bondar is currently the deputy director of the courts department at the Russian Supreme Court.