Gans joins from Publicis Groupe digital agency Razorfish, where he was the head of strategy and planning.
He replaces Adam Fulford, who left the agency last October to join Rufus Leonard as its executive planning director.
During his time at Razorfish, he was the global strategic lead on the Blackberry account as well as overseeing planning for Amnesty International, Asda and Unilever.
Prior to his spell at Razorfish, Gans was the head of web design at Comet and the head of catalogue operations at Boo.com.
Gans said: "These are exciting times for interactive design and for Grand Union. I relish the opportunity to add fresh strategic zeal to the continued growth of the agency and our clients."
Grand Union, which has clients including Boots, Butlins and Waitrose, was founded in 2000 by Rob Forshaw and Matt Nicholls. In 2010, it was sold to digital network FullSix Group in an estimated £15m deal.