The store will cover 55,000 sq ft (5,110 sq m) and sit alongside Debenhams and New Look.
The£220 million scheme will provide 450,000 sq ft (41,805 sq m) of new retail space, as well as a cinema, hotel, restaurants, 250 apartments and a bus station.
Modus leasing director Nigel Poad said M&S will double its trading footage in Newport. “We have a number of other deals in solicitors’ hands with major fashion operators, which will strengthen the overall retail offer in the city,” he added.
Construction is set to start on site in spring and it is expected to be completed in 2010.
Letting agents on the scheme are Lunson Mitchenall and Tushingham Moore.