The hearing was cancelled in the last minute on Wednesday.
Among the activists are Loujain al-Hathloul, Eman al-Nafjan and Aziza al-Yousef.
A court official informed some of the relatives that the session would not take place, citing the judge’s "private reasons."
No new date has been announced, Presstv Reported.
Diplomats and foreign media, already barred from attending previous sessions in the high-profile trial, were turned away from the criminal court of Riyadh.
In May 2018, more than a dozen activists were arrested on suspicion of harming national interests and offering support to hostile elements abroad.
At the time, international rights groups reported the detention of prominent female activists among the detainees. The women had previously campaigned for the right to drive and an end to the kingdom’s male guardianship system that renders women second-class citizens.
Several of the women are said to have been held in solitary confinement for months and faced torture and sexual harassment.
Saudi authorities have labeled the detainees "traitors." The designation has infuriated rights activists in the country who fear additional arrests amid much-hyped reports of reforms led by Saudi Crown Prince Mohammed bin Salman.
The reforms have been accompanied by a heavy-handed crackdown on dissent, which has targeted clerics as well as some of the very female activists who campaigned for years to end the driving ban.
The regime in Riyadh is also under fire over the murder of dissident journalist Jamal Khashoggi at the Saudi consulate in Istanbul on October 2, 2018.
Khashoggi, a distinguished commentator on Saudi affairs who wrote for The Washington Post’s Global Opinions section, was tortured and killed.
In a separate development on Wednesday, two Saudi sisters in their 20s, who have fled abuse in their country and are currently in Georgia, took to Twitter to plead for international protection.
They say their lives would be at risk if they returned.
The girls said they needed help from the international community to find a new country to call home. Maha al-Subaie and Wafa al-Subaie said they were seeking protection from the United Nations refugee agency (UNHCR).
"We are in danger. We need your support to deliver our voice. We want protection. We want a country... (that) welcomes us and protects our rights. Please help us," the pair wrote on a shared Twitter account named GeorgiaSisters.
Earlier this year, an 18-year-old Saudi girl made global headlines by locking herself inside an airport hotel room in Bangkok after fleeing domestic abuse by her own family. She was later granted asylum in Canada.
Last year, two Saudi sisters were found dead while duct-taped together in New York’s Hudson River.