The agency takes on the account immediately and will handle Habitat’s brand positioning and strategic communications. The agency will work with the retailer’s in house design team.
Portas beat Antidote in the final stage of the competitive process for the business.
Habitat hired Now to handle its advertising and social media account in June 2012. Now was not involved in this most recent pitch but might still work with the brand in the future.
Jocelyn Dowden, the head of marketing for Habitat, said: "Portas is an agency with such a strong retail expertise combined with an unparalleled understanding of people's experience of brands.
"We believe the agency has what it takes to help support us articulate this great British brand to a wider audience and support our future expansion strategy."
Home Retail Group, the owner of Homebase and Argos, bought the Habitat brand and three London shops in 2011 for £24.5 million. The retailer now sells its products online, in mini store areas in Homebase shops and through Argos.
Mary Portas, the chief creative officer at Portas, said: "Habitat is a perfect fit for our agency as like us they believe that a powerful communication can only work if it touches all parts of the brand that people experience.
"We believe in this business and its enormous potential and are looking forward to a great journey together."
Last year Portas brought in Helen Weisinger, the former chief marketing officer at EDC, as marketing partner to join David Wood, the former business director at WPP's Team Vodafone, in a bid to expand its profile and the work it does for clients.