A judge handed Benzema a one-year suspended jail term and ordered him to pay a €75,000 (£63,000; $84,000) fine.
Benzema, 33, was one of five people put on trial last month over an attempt to extort Frenchman Mathieu Valbuena.
The scandal has stunned the football community in France and both players lost their national team places.
The case dates back to June 2015, when the two footballers were at a French training camp.
At the camp, Benzema put pressure on Valbuena to pay off the blackmailers, whom he had conspired with to act as an intermediary, prosecutors said.
Benzema has always denied the allegations and insisted he was only trying to help Valbuena get rid of the compromising video.
Benzema was not present in court in Versailles for the verdict, nor was Valbuena, who plays for Greek club Olympiakos.
Four of Benzema’s co-defendants in the trial were also found guilty on Wednesday. They were handed jail sentences ranging from 18 months suspended to two-and-a-half years in prison.
Benzema’s lawyers said they would appeal his conviction. “The reaction is ultimately an angry one to this judgment which is perfectly contradictory,” his lawyer, Sylvain Cormier, told reporters outside court.
But when delivering the verdict, the judge said Benzema had “implicated himself personally, through subterfuge and lies, to convince his teammate to submit to the blackmail”.
Benzema made a surprise comeback to the French national team in May, five years after he was exiled from the side when the allegations first surfaced in 2015.
But last month, the French football federation said a guilty verdict would not necessarily jeopardise Benzema’s position in the national side.
For his performances on the pitch, Benzema was named a candidate for the Ballon d’Or footballer of the year award which will be announced next week.
Case leaves Real Madrid status intact
There are two ways of dealing with the private lives of footballers and we have seen that in the case of Benzema. The story hasn’t been given much importance in the sports media in Spain, but it has been hugely prominent in France.
In France, Benzema will be questioned professionally because of his behaviour off the pitch, much more so than in Spain. In France, private lives are more relevant, not just in sport but also in politics.
Benzema – who is of Algerian descent – has suggested there was an element of racism in this case. He felt that, had he been a white player, he would have been treated differently.
But none of it affects his status at Real Madrid, at all. In Spain, there is a view that your private life is your private life, and there has even been a strong campaign in the Madrid media for him to win the Ballon d’Or.
What is this case about?
It began in 2015 when Valbuena, now 37, asked a man in Marseille, Axel Angot, to upload the contents of his mobile phone to a new device.
Mr Angot found sexually explicit material on the phone. He and another defendant in the trial, Mustapha Zouaoui, were accused of trying to blackmail Valbuena by threatening to make the tape public.
Mr Zouaoui told reporters he had shared the tape, but there had never been an attempt to extort money.
Valbuena described being approached by another defendant, Younes Houass, who told the court he had warned the player about the issue without asking for money.
When the footballer went to the police, they set up a sting operation involving an undercover agent.
Prosecutors said another defendant was then brought into the scam – Karim Zenati, who is a childhood friend of Benzema. At this point, Benzema was asked to act as a “middleman” in the scheme, prosecutors said.
In October 2015, Benzema approached his fellow France player in his room at the national team’s training camp.
Benzema said he had merely tried to help his teammate dispose of the x-rated video, warning him: “Be careful, Math, they’re big, big thugs.”
He then offered to put him touch with someone he could trust – his childhood friend, Mr Zenati.
Police were by now tapping their phone calls and recorded Benzema telling his friend: “He’s not taking us seriously.”
Mr Zenati is said to have replied: “We’re here to sort it out; if he doesn’t want that he’ll have to deal with the piranhas.”
Giving evidence at the start of the trial, Valbuena said he had never considered handing over money to stop the video getting out.
Unlike his former teammate, Valbuena has not played for France since the scandal began.
Testifying during the trial, Valbuena told the court that football was his life.
“I knew if that video got out it would make things difficult with the French team,” he said.