The agency said Collin will "add depth" to its "strategic planning capabilities" given the increasing amount of business following the Accenture Interactive deal.
It means Collin will reunite with Jon Wilkins, executive chairman at Karmarama. In 2000 the duo, along with the late John Harlow, co-founded Naked, which closed its doors in London earlier this month.
Collin, who has not been assigned to any specific accounts just yet, will report to Sid McGrath, chief strategy officer at Karmarama. Collin has also worked at PHD and BMP DDB.
Wilkins said: "Having worked with Will at BMP DDB, PHD and of course Naked, it’s only right and fitting to continue that trend and work with Will again."