ELC head of marketing Tracey Walker said Starfish's work will also include handling PR for product promotions and store openings.
A four-strong Starfish account team, which is headed by joint managing partner Julien Speed, reports to ELC external comms manager Katharine Shetler-Jones.
Speed said Starfish - which begins work on the account next month- would also seek to promote ELC to organisations such as parenting charity National ChildBirth Trust and pregnancy guide Emma's Diary.
ELC - which opened its first store in 1974, growing to 266 outlets nationwide - also offers its products for sale through mail order, the internet and some Sainsbury and Debenhams stores.
On the retail side, ELC competes with chains such as Mothercare, Woolworths, Argos and Toys 'R'Us. On the manufacturing side, its rivals include Tomy and Fisher-Price.
Starfish beat three-year incumbent agency The Red Consultancy and one other undisclosed agency in the pitch, which was held last month.
Walker said that the repitch had been held 'as part of ELC's standard three-year review policy' and did not indicate dissatisfaction with The Red Consultancy.