Robertson is looking at starting his own creative marketing business that would target social media and new advertising channels.
The 18-year Paddy Power veteran was promoted to group director of advertising last year after the Paddy Power-Betfair merger, having previously been director of brand engagement.
He was Paddy Power’s head of mischief between 2011 and 2014, and is credited with building the bookmaker’s irreverent public profile to where it is today.
Most recently, as the group’s advertising director, he was responsible for overseeing a team of 50 ad specialists, and managing creative ideation through to delivery of completed campaigns for both Paddy Power and Betfair brands in multiple markets.
His departure comes after a wider shake-up within Paddy Power Betfair’s marketing department last year following the departure of Paddy Power chief marketing officer Gav Thompson, who was replaced by Betfair CMO Jonathan Devitt.
Paddy Power would not comment on whether Robertson would be directly replaced.
Robertson said: "I've massively enjoyed 18 mischief-filled years building one of Ireland's and the UK's edgiest, most politically incorrect brands.
"From sky tweeting above the Ryder Cup in the US to taking bets on the next Pope in St Peter's Square and managing a team of renegade social media misfits, it has been an extraordinary journey.
"It's time now to take what I've learned into my own space where I plan to work with other like-minded individuals and brands to continue to push the boundaries of creativity.
"I'm hugely indebted to the team at Paddy Power Betfair for their trust and backing over the years and for being so supportive with this exciting new chapter in my career."