The win, backed by an estimated £2 million budget, will be a consolation prize for the agency, which last year missed out in the pitch for the main £14 million Muller yoghurt and desserts business.
It also renews M&C Saatchi's working relationship with Andrew Harrison, the former Nestle Rowntree marketing chief, who is now Muller's managing director.
In 2001, Harrison went outside Nestle's agency roster to appoint M&C Saatchi for the launch of the All Stars chocolate assortment box. He worked with the agency again when Nestle struck a £6 million deal with ITV to link its confectionery brands to the 2003 series of Pop Idol.
However, Harrison chose TBWA\London ahead of M&C Saatchi to succeed Publicis on the main Muller account. TBWA declined to pitch for Cadbury desserts, fearing conflict with the Masterfoods business it won from Grey last year.
Muller took over the sales and marketing of Cadbury desserts in May last year.
The licence was previously held by Uniq Prepared Foods, which continues to manufacture the Cadbury-branded products.