The court said Abdul-Rahman al-Qaradawi and two other defendants were found guilty of spreading false news that harm state security, the source said on condition of anonymity due to restrictions on talking to the media.
The three were also ordered to pay a $30 fine each. Tuesday’s verdict is still subject to appeal.
Qaradawi’s son was previously slapped with a 3-year jail term on charges of spreading false news.
He is also sought by the authorities to stand trial on charges of offending the judiciary, in which former president Mohamed Morsi and 23 others are being tried.
Egyptian authorities have launched a harsh crackdown on supporters of Morsi and his Muslim Brotherhood group following a 2013 coup, killing hundreds and sending thousands behind bars.