Abdullah ah-Zaher became the youngest person given the death sentence, according to campaigners Reprieve.
Campaigners claim Abdullah ah-Zaher, who attended the protest when he was 15 years was put on death row as part of a crackdown on political dissent.
The now 19-year-old has been moved to solitary confinement and could be beheaded at any moment.
Despite possible repercussions, his family have gone public with his story, in a final bid to save his life.
His father Hassan al-Zaher said:
“Please help me save my son from the imminent threat of death. He doesn’t deserve to die just because he participated in a protest rally.”
According to the campaign group, Reprieve, Abdullah was arrested for being in the area of a protest in March 2012, beaten by police and tortured.
He was then allegedly forced to sign papers police fabricated. Saudi media reports suggest 52 prisoners will be executed at any time.
Abdullah was held alongside Ali al-Nimr, who has been sentenced to a death penalty for allegedly instigating a revolution using his Blackberry.
A Reprieve spokeswoman said:
“What we know from the families of the three is that they are in solitary confinement and being prepared for execution.
“They have been moved and undergone medical examinations, which seem to suggest their beheading is imminent.