The killing of Danish student Louisa Vesterager Jespersen, 24, and 28-year-old Norwegian Maren Ueland in December was deemed a "terrorist" act by Moroccan authorities.
Twenty-four defendants will face trial -- for charges including promoting terrorism, forming a terrorist cell or causing premeditated harm to persons -- in Sale, a city neighbouring the capital Rabat, defence lawyer Saad Sahli told AFP.
A Spanish-Swiss man who authorities allege subscribed to "extremist ideology" stands accused of helping the four main suspects in the murder, charges he denies.
The decapitated bodies of the two victims were found in the High Atlas mountains, where they had been hiking in an area popular with tourists.
A video circulated on social media allegedly showed the murder of one of the women, while Rabat's prosecutor has said the four main suspects appeared in separate footage pledging allegiance to the Islamic State group.
The accused however had no contact with the jihadist group in conflict zones, according to Morocco's anti-terror chief.
The North African country relies heavily on tourism.
Foreign visitors were previously targeted in a 2011 bomb blast in Marrakesh which killed 17 people.
An attack in 2003 on the financial capital Casablanca left 33 people dead.