The John Lewis store on London's Oxford Street has been wrapped with an asymmetric British flag, while a banner displaying a medal made out of items shoppers can buy in John Lewis has gone up at Stratford.
The retailer has also worked with fellow London 2012 partner Adidas to install giant banners and wraps at both its Cardiff and Sheffield shops.
An 80-foot image of Team GB athlete Tom Daley is on display across the front of John Lewis Cardiff, while shoppers at John Lewis Sheffield are greeted by a 40-foot image of Team GB athlete and local girl Jessica Ennis.
The idea for the project was devised by Omnicom's Manning Gottlieb OMD and the banners were realised in conjunction with Posterscope's Hyperspace and large-format outdoor media owner BlowUp.
Visitors will be directed to the official Olympic departments, which have been set up in branches of the stores to sell branded Olympic goods such as Wenlock and Mandeville soft toys.
The banners are part of a wider campaign aimed at targeting both domestic and international tourists while they are out and about around the Olympic venues and travelling around the capital.
Other marketing activity from John Lewis includes press ads in the official Olympic programmes, traditional and digital sites on the London Underground and press ads in conjunction with Adidas and Panasonic.
At the Winter Olympics in Vancouver in 2010, department store Sears wrapped its stores in the red and white of the Canadian flag to show its support and affiliation with the Games.