The appointment marks the end of Publicis' 17-year relationship with MFI.
In July, MFI revealed revenues from its retailing arm had fallen by more than 25 per cent in the first six months of the year.
The switch in agency arrangements also comes after the sale of MFI's 200-store chain to Merchant Equity Partners (MEP) for the token sum of £1 in September.
MEP also holds a stake in the computer retailer PC World, which already uses M&C Saatchi for its advertising.
MFI's media planning and buying account is expected to remain at ZenithOptimedia. M&C Saatchi and MFI declined to comment.