City, which was co-founded by Lord Willie Haughey, will fulfil building and service maintenance needs for more than 650 M&S stores, offices and distribution sites from 1 April.
This includes a dedicated 24-hour helpdesk and a computer aided facilities management system.
Its headcount has been boosted by 130 new recruits and around 450 employees who transferred from sub-contractors which were previously carrying out the work for M&S. A significant portion of these will be based in Glasgow.
Financial details of the deal were not disclosed.
City chief Michael Hughes said: “This is a fantastic opportunity to extend our retail footprint with one of world’s leading brands. I look forward to a long and successful partnership with M&S.”
The firm has more than 13,000 employees across the UK, France, Australia, Asia, the US and Malaysia.
Ian Moore, head of store development and facilities management for M&S said: “As part of our transformation efforts we’re delighted to be partnering with City to deliver a more efficient approach to facilities management.
“City’s experience and best in class system will improve maintenance service levels across our stores, distribution sites and offices helping us to deliver a better shopping experience for our customers.”