Saad Eddin Ibrahim, an outspoken critic of the Egyptian government, has been sentenced to two years in prison.
The sociologist and human rights activist was convicted for "tarnishing Egypt's reputation," the country's official MENA news agency said.
Shady Talaat, Ibrahim's laywer, said the ruling by a Cairo court was flawed and that he would use his right to appeal.
Ibrahim was granted bail of 10,000 Egyptian pounds ($1,890).
Ibrahim, who has been living in Qatar since June 2007, says he fears arrest if he returns to Egypt.
The case is among a series of lawsuits filed by members and loyalists of Egypt's ruling National Democratic Party (NDP) against government critics.
Prosecuting lawyers Abul Naga al-Mehrezi and Hossam Salim took the case against Ibrahim to court and accused him of defaming the country after a series of articles and speeches on citizenship and democracy in which he criticised the Egyptian government.
Ibrahim said last month he wanted to return from exile, but only after assurances he would not be arrested.
According to the Egyptian independent daily Al-Masri Al-Youm, Ibrahim had written to the foreign ministry asking for guarantees that he would not be held on arrival.
The 69-year old went into exile citing a climate prejudicial to political opposition and human rights.
A vocal critic of Hosni Mubarak, the Egyptian president, Ibrahim was quoted in the Washington Post last year as saying he preferred to remain outside Egypt for fear of being arrested "or worse".
After meeting George Bush, the US president, in June last year in Prague he was called a "dissident" by the US leader.
Ibrahim, who founded the Ibn Khaldoun Centre for Development Studies, was sentenced in 2001 to seven years for, again, "tarnishing Egypt's reputation," before being freed on appeal after spending 15 months behind bars.