Saayid bin Zuair was convicted for "sowing sedition and inciting disobedience to the ruler", his son said on Sunday.
The scholar, who was denied access to a lawyer, will appeal against the Riyadh court's verdict, said his son Abd Allah, who attended the hearing on Sunday along with a handful of close relatives and a human-rights representative.
"The verdict was announced in the absence of a lawyer," who was never appointed, Abd Allah said after the more than two-hour session.
"The judge said there was no need for a lawyer according to Sharia (Islamic law)," he said.
After the verdict was read, plain-clothed police officers scuffled with members of Zuair's family and friends who tried to approach the defendant as he was led out of the judge's quarters.
Muflih al-Qahtani, representative of the Saudi National Human Rights Association (NHRA), who was present during Sunday's session, said it had "followed the usual practice".
Commenting on the restrictions concerning public access to the trial, al-Qahtani, who along with another NHRA member was barred from attending last week's hearing, said a judge had the discretion to hold trials in camera.
''The judge said there was no need for a lawyer according to Sharia (Islamic law)''
Abd Allah bin Zuair, son of Saayid bin Zuair
The Interior Ministry said in April that 54-year-old Zuair, who is considered a hardliner, had been detained because of remarks in which he backed bombings in Riyadh that targeted Muslim and non-Muslim residents.
In a 15 April appearance on Aljazeera, the former professor of mass communications "described the terrorist acts committed by the deviant group as being directed at non-Muslims, condoning the killing of Muslims [in the process] by those who carry them out", an official said.
However, judge Saad al-Shaddi made no reference on Sunday to Zair's comments on human bombings, the son said.
"The judge did not go into the details of my father's comments to the press. He said the five-year sentence is a punishment merely for his appearance on Aljazeera and speaking in a mosque," he said.
"Addressing the public leads to sowing sedition," he quoted the judge as saying.
The kingdom has been shaken by
a wave of bombings and killings
The prison sentence was the second for Zuair who was incarcerated between 1995 and 2003 without being charged.
According to his son, Zuair rejected the verdict and denied the charges, asking the judge what he had based his verdict on.
He said his father argued that the verdict was devoid of any specific charges and reminded the judge that he "did not give his lawyers the chance to defend him".
Last week's hearing was adjourned as the defendant had refused to enter a plea in the absence of a lawyer.
The son blamed al-Hair prison, where Zuair is being held, for not allowing his father to appoint an attorney.
Three Saudi reformists are in custody pending trial for calling for constitutional changes.
Only one hearing in the case of Matruq al-Falah, Ali al-Dimaini and Abd Allah al-Hamad has been convened since their arrest in March. The second hearing was postponed due to the large number of people who wanted to attend.