The US toy manufacturer, which manufacturers the Barbie doll and Scrabble among others, is meeting agencies at the end of the month, according to sources close to the situation.
After the meetings have been concluded, Mattel will issue a brief and draw up a shortlist of agencies. Sources said the process is part of a statutory review.
MindShare handles Mattel's media duties in the majority of European markets including the £10m UK business, with the exception of Eastern Europe.
The creative account, handled by Ogilvy & Mather, is understood to be unaffected by the media review.
Mattel's net sales grew by 7% in the third quarter last year from £880m to £940m, and included the third consecutive quarterly sales rise for the Barbie brand.
Last year, the company relaunched Barbie's boyfriend Ken and rolled out a Barbie cosmetics range in partnership with Estee Lauder brand Mac, to boost flagging sales.
Although Barbie is one of Mattel's strongest brands, the company is facing strong competition from rival doll brand, Bratz. There is also renewed competition from rival Sindy, who was last year given a £3m relaunch by makers Pedigree Toys.
Last month, Mattel hired Dialogue to create and manage a loyalty marketing scheme for its Barbie brand, as it attempts to encourage consumers to buy more Barbie prodocuts.
At the time of writing, Mattel was unavailable for comment.