The 32m-long vehicles will operate in pairs, accommodating up to 606 passengers. Assembly will take place at Alstom's La Rochelle plant in France and deliveries will start in July 2017.
The order will be 65%-financed by the French government through the Reserve for Emerging Countries (RPE), with the remaining 35% coming from the Moroccan government.
The 22.5km Line 2 will link Ain Sebaa in the east with the city's main hospital in the central district of Hermitage, running via El Badr, Laayoune, and Mers Sultan and interchanging with Line 1 at Abdelmoumen and Ibn Tachfine stations.
Preparatory construction including utilities diversion works began in May and major construction is scheduled to start next May.
Meanwhile, Line 1 will be extended 2km from its current southern terminus at Facultès to Laymoun and Lissasfa.
The Dirhams 3.7bn ($US 380m) expansion project is due to be completed by 2019.
Alstom has already supplied 74 Citadis LRVs for the 31km Line 1, which opened in December 2012.