The agency beat TBWA\Upstart and Grey to clinch the business.
Its debut TV offering will break at the beginning of September to promote the third series of Stephen King's The Dead Zone and the UK premier of the US reality show Mad Mad House. It will be supported by press and radio advertising.
Eleanor McBrien, the marketing director at the Sci-Fi Channel, said: "We chose Quiet Storm because it understands our brand and is passionate about the fun, humour and universal themes that are inherent in our programming.
"The work it will be undertaking will express those values through distinctly quirky marketing communications."
Quiet Storm's appointment follows the £2 million repositioning of the Sci-Fi Channel back in April this year as a more mainstream offering.
The traditional interpretation of the genre has been broadened to add fantasy and paranormal programmes to the channel's mix.
Media was unaffected by the review and will continue to be handled by Rocket.