The poster, promoting the brand's new D to G cup size range of bras, is a mosaic of photos that form a much larger image of a woman in her Wonderbra.
The images were sourced last month, when Wonderbra invited women to attend an underwear shoot in London or upload images of themselves on to the company's website.
Iris created the campaign, which also includes an online element, where users can interact with the billboard and zoom in on the individual chest shots.