The three have been detained since 2019 and are facing separate allegations over the Hope coalition case, in which authorities accused them of being part group funded by the Muslim Brotherhood to incite revolution and commit violence.
Colleagues and activists said the arrests were aimed at preventing the formation of a secular coalition ahead of parliamentary elections in 2020 that were dominated by supporters of President Abdel Fattah al-Sisi.
The detentions have become one of Egypt's most high-profile human rights cases.
Wednesday's verdict by a state security court cannot be appealed. Along with journalist Hisham Foad and political activist Hossam Moeness, who were sentenced to four years, two other suspects received two-year terms, the judicial source said.
Eight human rights groups condemned the ruling, noting that it came despite Sisi's recent decision not to renew Egypt's state of emergency and the government's publication of a national human rights strategy.
"Today's ruling came to confirm that the government's anti-human rights policies will remain in place," the Cairo Institute for Human Rights Studies and seven other groups said in a statement.
Since becoming president in 2014, former army chief Sisi has overseen a crackdown that has swept up liberal opponents as well as the Islamists whose overthrow he had led a year earlier.
Rights groups say tens of thousands have been jailed.
Sisi has denied holding political prisoners and his backers say the measures were necessary to stabilise Egypt.
(Reporting by Haithem Ahmed and Aidan Lewis; Editing by Giles Elgood)
