Falkirk Council's licensing board agreed to grant a licence that will allow the store to double the floorspace where alcohol is displayed, as part of the major refurbishment.
Members heard that its wasn't just off-sales that would get more space in the shop in Central Retail Park and that work on the expansion - which starts this month - will be finished by August.
Marks and Spencer announced in February that it was taking over the unit next door, formerly Tapi Carpets.
Representing the business, Christopher Grunart told the board that the store would no longer require an on-sales licence as the cafe was closing.
He said: "This is part of a national repositioning of the stores, it is recognition by M&S that the principal purpose of visiting their stores is food and groceries.
"Although the cafes were used, they were perhaps underused and less in demand.
"What our customers want, we feel, is a greater choice and more products and more lines to be available in store.
"The increase in off-sales will allow us to add a number of ranges, some of which are currently unavailable in Falkirk."
Licensing convener Niall Coleman said he was concerned at the sharp increase in floor space devoted to alcohol sales, which will more than double.
He was assured there would be lots of staff around the area and it would be well covered with CCTV.
Mr Grunart said: "It's an increase in area, yes, but Marks and Spencer are not willing to accept an increase in anti-social behaviour or an increase in loss - we want to keep those suppressed at all times.
"The aim is to keep the store in its current manner, which is well run and operated."
General manager Brian Torley added: "It is a predominantly grocery-based expansion, because that's where the market is for us now," he said.
He explained that other sections that will more than double their space include biscuits, world foods, frozen food and confectionary.