The Leo Burnett-owned agency won the account following a competitive pitch. The agency is not currently on the BSkyB roster.
Engine-owned Jam, which works on the BSkyB digital account, was the incumbent on the business.
Holler will begin working on the account immediately, with a campaign due to launch in the spring.
James Kirkham, co-founder of Holler, said: "We are looking forward to implementing a cutting-edge social strategy to make this new brand stand out."
Now TV, which offers instant access to Sky Movies without a contract, set-up costs or installation, won a trademark battle over its name in November 2012, when a High Court judge threw out a challenge from a Hong Kong-based telecoms company.
Sky’s launch of the non-contract Now TV service was one of the reasons why the Competition Commission decided not to place restrictions on the pay-TV film market, alongside the arrival of LoveFilm and Netflix.
Publicis Groupe bought Holler for an undisclosed sum in February 2011 and put it within the Leo Burnett Group. It has since picked up business such as the Peroni Nastro Azzurro UK digital account.