The irreverent showbiz site was recently voted in the Top Ten of the world's coolest websites by Coolbrands and has scooped the nationals with a series of exclusives.
The new-look site launches on 28 October and will include an expanded picture gallery, review section and an online TV channel, featuring celebrity interviews, round-ups and event coverage.
Taylor Herring will handle a consumer campaign for the launch focusing on exclusive news stories and content. Online publicity will be handled by Force 10, the agency's digital division.
The agency will work with the site's digital media partner Perform, which bought an undisclosed shareholding in the site earlier this year.
Holy Moly was created in 2002 and attracts more than one million unique users a month. It claims to have broken the story about Cheryl Cole getting The X Factor job. The site is updated daily alongside a weekly mail-out.
Taylor Herring recently helped launch US comedy site Funny or Die.