
It is believed that the work will centre on the brand's plans to move upmarket to challenge rivals such as Mamas & Papas.
The retailer's main advertising account, currently held by St Luke's, is also under review. However, BBH's appointment is a separate one-off project.
In 2007, Mothercare acquired educational toy chain ELC in an £85m cash deal.
At the time, chief executive Ben Gordon said he planned to create dozens of 'centres for parenting' by incorporating ELC into Mothercare's bigger stores.