Universal McCann and PHD were also involved at an earlier stage of the pitch process.
It is not clear if MediaCom, the incumbent on Nokia’s European, Asian and US accounts, repitched for the business.
Carat is expected to commence work in the third quarter of the year.
In April, Nokia posted a 90% drop in first quarter profit. Net profits fell to €122m (£108m) during the quarter, which is a marked decline from the €1.2bn (£1.06bn) it reported in the same period last year.
Sales also fell by 27% to €9.28bn (£8.2bn), compared to €12.7bn (£11.2bn) a year ago.
Earlier in the year the handset maker announced plans to cut 1,700 jobs globally.
Nokia recently launched an online campaign to promote the N85 handset as a gaming device.
The “Game Over Boredom” campaign, created by Work Club, features a dog which plays, rips up newspapers and acts as a friend to position the phone as a way to beat boredom.