In an open letter to Moroccan Prime Minister Aziz Akhannouch, whose signature is needed for the extradition to be carried out, the rights groups - including Amnesty International and Human Rights Watch - said the family of Saudi activist Hassan al-Rabie had "long been persecuted by the Saudi authorities".
If returned to Saudi Arabia, "he faces credible risks of persecution and other serious harm, including a risk of torture, for reasons related to his religious beliefs and his family's history of political protests," they wrote.
A Moroccan court earlier this month ruled in favor of the extradition of al-Rabie, a member of a family of activists from the country's Shia minority, after he was detained in the North African kingdom.
"We believe that Hassan's detention and extradition are part of the Saudi authorities' reprisals" against the family, the 24 rights groups said Monday, adding he was "likely to face serious human rights abuses upon his arrival to Saudi Arabia".
They added that the Moroccan court issued its ruling "following a single hearing that appears not to have allowed (Rabie) reasonable time to present his case for protection".
The Rabie family hails from eastern Saudi Arabia, home to a large Shia community that complains of systematic discrimination by the kingdom's Sunni-dominated authorities.
Hassan al-Rabie, 26, was arrested at Saudi Arabia's request on January 14 as he tried to leave Morocco for Turkey, according to his brother Ahmed, who said Riyadh was trying to exert pressure in order to find a third brother, activist Munir.
The kingdom sentenced their older brother Ali to death in November, allegedly for helping Munir escape Saudi Arabia, according to MENA Rights Group, a Geneva-based legal advocacy organization.
Rare demonstrations took place in eastern Saudi Arabia in the wake of the Arab Spring uprisings of 2011, followed by violent clashes between protesters and security forces there in 2017.
In March last year, the kingdom executed 81 people in single day, many of them from the Shiite minority -- including two of Rabie's cousins, according to MENA Rights Group.