Ryan joined Karmarama in July 2013 with a brief to bring together the creative departments of Karma Communication Group’s agencies, which include Crayon, Kream and Krowd.
Her departure follows the appointment of Nik Studzinski as the chief creative officer, replacing the Karmarama founder Dave Buonaguidi.
Jon Wilkins, the executive chairman at Karmarama, said: "Caitlin is such a fabulous person. She has helped us build a truly media-neutral, modern creative department, as well as improving our digital and data credentials.
"We wish her the very best and thank her for helping the agency go from strength to strength."
Ryan was previously the executive creative director at Proximity London.