Previously of retailer Gap, Hicks joined at the start of 2016. Before that, she was a partner at agency Brunswick.
In an email to staff this afternoon, Sky group CEO Jeremy Darroch thanked Hicks for her work, saying she would "move on to something new" but would remain "available on a consultancy basis" to Sky for the first six months of 2018.
Darroch said the business would announce a replacement in the New Year.
Hicks was one of 12 members of Sky's group executive team. She had five people reporting to her, including director of corporate comms Gavin Davis, who joined from Bell Pottinger in September last year.
Davis' arrival followed the departure of longstanding external comms chief Robert Fraser earlier in May 2016.
Sky has spent the last year in corporate limbo over a controversial potential sale to minority owner Fox, which is currently being scrutinised by UK regulators.
On Wednesday, the House of Commons' Digital, Culture, Media, and Sport Committee will hold a pre-appointment screening with Lord Burns, who is the Government's preferred candidate for chair of media regulator Ofcom. Issues on which MPs will question Burns include the potential Fox/Sky merger.