The insider's guide, from travelers who've actually been through.
The ONCF train is the right call. The station sits inside Terminal 1, trains run hourly to Casa Voyageurs, and the ride takes 33 minutes. Second-class tickets cost 43 MAD, which is genuinely cheap. Taxis are metered and will run you 250-300 MAD with a 30-45 minute ride depending on traffic. The train wins on both price and predictability.
Before your layover here
Some links are affiliate links. Booking through them supports MyLayover at no extra cost to you.
CMN is a working airport, not a showcase. Royal Air Maroc bases here, so the terminal is built around their operation. Lounges are geared toward RA passengers and alliance partners, food options are limited but present, and duty-free retail covers the basics. The terminal gets busy during Royal Air Maroc departure banks, so build in time if you are connecting on a tight window.
The math on leaving is unforgiving. Getting from the plane to Casa Voyageurs and back to a security-cleared gate requires roughly 2.5 hours of overhead: 45 minutes through immigration, 33 minutes on the train each way, plus 55 minutes back through security. That is before you step outside the station. On anything under 6 hours, do not leave the airport. Three hours is a firm no. Four or five hours is still a no. Once you clear 6 hours, you can reach the city and actually see something. At 10 hours or more, you are comfortable.
Fill out the arrival form on the plane. There are no eGates for foreign passport holders and queues can back up quickly after overnight arrivals. Currency is Moroccan Dirham (MAD); exchange counters are available in the terminal.