The defendants include three suicide-bombers who survived the attack aimed at foreign and Jewish targets in the kingdom’s commercial capital.
It is the first in a series following an investigation of the banned Salafia Jihadia group by Moroccan authorities.
The group stands accused of masterminding the attacks and 200 of its members have been linked to the bombings which shook Casablanca on 16 May.
Bombers call for social reform
One of the bombers, Mohammad al-Omari, justified his participation in the operation, saying the attack was made to highlight increasing social inequality in the north African country.
Proceedings against a number of other suspects were immediately suspended to give the defence more time to gather evidence. Still, the three would-be suicide bombers, named as Mohamed el Omari, Abou Zoubeir and Rachid Jalil, continued.
The remaining accused will be tried in courts in Casablanca, Rabat, Kenitra and Tangiers in coming months. Those convicted face the death penalty.
The prosecution claims Salafia Jihadia is linked to Osama bin Laden’s al Qaeda.
On 12 July ten suspects found guilty of playing a role in the fatal bombing were sentenced to death. A further 21 were locked up for between a year and life.