Ibrahim Issa and Sahar Zaki of the opposition Al-Dustour newspaper were sentenced on Monday at a court in the village of al-Warrak, near Cairo.
The group said the sentence was "a serious setback for press freedom".
In April 2005, Al-Dustour reported on a lawsuit against Hosni Mubarak, the Egyptian president, which accused him of misusing public funds during the privatisation of government owned companies.
The man who brought the lawsuit, Said Muhammad Abdullah Sulaiman, was also sentenced to one year in prison.
Joe Stork, a Human Rights Watch deputy director, said on Wednesday: "Jailing Ibrahim Issa is an obvious attempt to punish a persistent government critic and to stop others from speaking out."
In 2004, Mubarak promised to change laws that allow journalists to be jailed for their work, but the government has not yet passed the required legislation.
Al-Dustour is one of a handful of independent and opposition newspapers that have campaigned for democratic reform in Egypt and challenged Mubarak's 25-year rule.
Three other Egyptian journalists appeared before a criminal court earlier this month for denouncing reported state-sponsored fraud during the 2005 parliamentary elections.