Company claims the move is the broadest in the industry.
Marriott currently supports mobile check-ins for 31 hotels and now plans to extend the functionality to 325 hotels, which it claims will represent the largest offering of its kind in the US and Canada.
The function is accessible through the Marriott app, with all member of the Marriott Rewards scheme able to check-in via their phone from 4pm on the day before their arrival, with push notifications sent when the room is ready.
Rewards users have card details stored securely within the app, which means they can walk up to a dedicated mobile check-in desk at the hotel and their key will be ready and waiting.
Paul Cahill, SVP of brand management for Marriott Hotels, said: "As Marriott developed the app and tested mobile check-in, we engaged customers, asking for their feedback to perfect the experience and learn what mattered most to them.
"Our frequent guests told us they wanted mobile check-in first, using their smartphones, to be widely available. That is what we are delivering as Marriott Hotels continues its journey of envisioning the future of travel for the next generation."
The company plans to expand mobile services outside of North America and into other countries, while future innovations are currently undergoing testing at selected hotels.