The move will see both groups continuing to operate independently, but coming together to work on specific projects. A spokeswoman for Iris says the two groups are already pitching together for work.
Iris works for companies including Adidas, Sony Ericsson and Shell and also created the Wenlock and Mandeville, the London 2012 Olympic and Paralympic mascots.
The Meredith Corporation operates magazines, television stations and websites, as well as integrated marketing arm Meredith Accelerated Marketing.
The groups say the partnership will create a combined asset pool of more than 4000 staff working in 25 offices across 13 countries.
Ian Millner, global chief executive and founder of Iris, says, ‘This is going to offer clients a real alternative to the traditional agency model and one that is fit for the “always on” world we now live in.’