Collier and Robinson joined JWT in 1999 and rose to become directors at the agency. The pair will work across all of CHI's clients, which include Britvic, Carphone Warehouse and British Gas.
At JWT, the team has produced work for clients including Shell, Kellogg and Nestle.
Last year, Collier and Robinson won two silver Campaign Press Awards for their print work for Exchange & Mart. The pair began their careers at Mother.
The hiring is the second by CHI's executive creative director, Ewan Paterson, since he joined the agency from Bartle Bogle Hegarty to oversee the day-to-day running of its creative department in November 2005.
Paterson said: "It's not often that you see a team where everything in their book is great. When you do, you have to hire them.
"They have incredibly high creative standards and the rare ability to create great work on big brands."
Earlier this year, Paterson signed Angus Wardlaw and Alexei Berwitz from Miles Calcraft Briginshaw Duffy to lead creative on the agency's Toyota business.