The Tokyo-based arm of the global design consultancy has designed the site, which will gather tweets in the run-up to its relaunch and offer reduced prices from 9-15 September.
Dentsu is Uniqlo’s preferred agency and was appointed to the work directly.
The new site will feature increased zoom levels, more product images and more customer account and delivery options.
The Lucky Counter feature will launch alongside a new YouTube channel, designed to showcase collections.
Uniqlo says the relaunched site is part of its UK development strategy, which will also see the brand open a new store in the Bluewater shopping centre in October.
The current website has been in place since June 2007.