It is the second Unilever win for Agency Republic this month, having earlier picked up the digital brief for Dove.
The agency initially has a brief to relaunch the Impulse website and make it more of an experience for visitors. It will also look at developing marketing campaigns via social networking sites.
The audience of 11- to 18-year-old girls that Unilever wants to reach is increasingly spending more time online, and Unilever wants to tap in to the brand engagement offered by digital marketing that isn't available through traditional media channels.
Javoneh Daneshpay, the brand manager for Impulse, said: "We were really looking for a forward-thinking digital agency that would reposition and bring the brand online. We appointed Agency Republic on the strength of its proven track record in delivering innovative solutions in the digital sector."
The Impulse business will be headed by the account director, Jacqui Smith.