The pair will reunite with their former executive creative director, Ewan Paterson, who left CHI to become the chief creative officer at DDB Chicago in April last year.
They will work across the agency's entire list of accounts including Starburst, Skittles and Milky Way, after Mars shifted a major portion of its advertising business into DDB Chicago in June.
Collier and Robinson began their careers working together at Mother, before spending seven years at JWT London.
At JWT, they worked on ads for Shell and Kellogg and appeared in Campaign's annual "Faces to Watch" feature.
They joined CHI in 2006, creating award-winning campaigns for The Sunday Times and "clever hamsters" and "Mr Memory" for Drench.
Most recently, the pair created "homes within homes" for TalkTalk.
Paterson said: "Matt and Wayne are one of the best teams I've ever worked with. It's no secret that they are in high demand, and I'm thrilled that they will be joining us here in Chicago."