Mohammed al-Qahtani, one of the dissidents most frequently quoted by western news media, received a 10-year sentence, The Wall Street Journal reported. Abdullah al-Hamed, who founded a civil rights organization with Qahtani, got five years.
The court dissolved the two men's organization after finding them guilty. They were immediately jailed after being allowed to remain free during their 10-month trial.
Activists, including the two defendants, said during the trial the Saudi government is trying to scare activists from using social media like Twitter.
"I think it's a campaign against all the human-rights activists," Waleed Abu Alkhair of Jeddah, who faces trial himself, said after the verdict.
The government said dissidents are using social media to foment violence.
"There are people who misuse social networking and try to send false information," Maj. Gen. Mansour Turki, a security spokesman for the interior ministry, said Friday.