The appointment extends the relationship between the university and FCB, as FCBi handles its below-the-line advertising.
It follows a pitch that also involved Clark McKay & Walpole, DFGW and Joshua.
FCB's brief will be to drive graduate recruitment and raise the profile and status of the Open University.
The Open University, the UK's largest university, launched in 1971 and has more than 200,000 students. They account for 22 per cent of all part-time higher education students in Britain.
Two-thirds of its students are aged between 25 and 44. More than a third of those starting courses have qualifications below conventional university entrance requirements. However, about 70 per cent complete their degrees.
Open University courses are available throughout Europe and in other parts of the world. About 26,000 students are studying from outside the UK.
No-one at FCB was available to comment.