Fahmy, who holds dual Canadian-Egyptian citizenship, has been granted a retrial, he said in the statement.
"The trial date on February 12 represents our worst nightmare, to have to go through another circus of a retrial," he said.
Fahmy was one of three Al Jazeera journalists arrested in Cairo in December 2013 and accused of being part of the country's banned Muslim Brotherhood.
Producer Baher Mohamed, who is Egyptian, also remains behind bars.
Australian Peter Greste, who was sentenced to seven years and spent 400 days in prison, was released last week.
On February 2, Clooney gave CNN a statement regarding Fahmy, who also used to work for CNN.
"I have been in touch with the Fahmy family and we are all delighted that Peter Greste has been released," it said. "As Mr. Fahmy's counsel we are doing all we can to ensure the same outcome for Mr. Fahmy, who has suffered the same injustice."
Fahmy's family shocked
Fahmy's fiancee, Arwa Emara, told CNN in December that she had hoped, before Fahmy's arrest, that they would have a "very simple life."
"I was very happy when I first met Mohamed," she said. "I felt that he's the one. And after his arrest, I found myself doing things that I never expected that I`m able to do."
Emara sent a letter at that time to Clooney requesting that Fahmy be released and sent to Canada.
For many months, Fahmy's family has tried to call attention to serious health problems the journalist is enduring in prison. Fahmy is suffering from a dislocated shoulder, they say.
The journalist's brother Adel Fahmy told CNN on Sunday that the Fahmy family is shocked and devastated by word of a retrial.
Adel Fahmy blames the Canadian government for failing to secure his brother's release.
"We have no clue what happened, but we are very upset with how the Canadian government has dealt with this case from day one," he said. "We had confirmations from highest sources that he would be deported in the coming days ... and all we got is false hope."
He said that his brother formally renounced his Egyptian citizenship because officials told him that if he did, he would be released.
"We don't understand why he has to stand in court when he has (renounced) his passport," Adel Fahmy said." That was the deal ... that he'd denounce his citizenship, that they (the Egyptian government) would not announce it to the media, but they did the exact opposite. They did announce it to the media and he is devastated that this is happening to him."
Mohamed Fahmy has a "permanent disability in his arm," his brother said, adding that because the journalist had been wrongly imprisoned, his "reputation has been severely tainted."
Australian Foreign Minister Julie Bishop said Greste's freedom was won "unconditionally."
The journalists were accused of supporting the banned Muslim Brotherhood, though each has maintained steadfastly that they did nothing wrong.
One of Greste's lawyers suggested days ago there could be more legal issues ahead for him.
"According to Egyptian law, this is considered an extradition," Amr Eldib said. "Peter must be tried in Australia and authorities there must determine if he is guilty or not."