The partnership will bring 4th Screen's rich-media ad formats, which include HTML5 formats and tap-to-expand banners, to Daily Mash's new mobile site, which launched at the weekend with Audi as one of the first advertisers.
Advertising sales for the Daily Mash desktop site will continue to be handled by w00tmedia.
Thedailymash.co.uk attracted 130,000 unique visitors in the UK during April, a decline of 6% year over year, according to comScore.
Mark Slade, chief executive of 4th Screen Advertising, said: "A growing number of publishers are waking up to the fact that mobile isn't just an add-on anymore, but is now at the forefront of modern publishing models."
In March, ITV appointed 4th Screen Advertising as its exclusive third-party mobile sales partner.
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