Elliott and Williamson had worked at the agency for just over five years, having joined from Mother London towards the end of 2005.
The pair came with a big creative reputation, having created award-winning campaigns such as the "Spike Lee" spot for Orange, and "over-friendly father" ad for Dr Pepper.
During their time at WCRS&Co, Elliott and Williamson made a number of changes to the agency’s creative department, including hiring Sid Lee’s Simon Schmitt, the man behind Adidas’ "house party" campaigns.
As creative directors, they have also overseen work for brands such as Sky, Weetabix, Transport for London and Brylcreem.
Elliott and Williamson’s departure follows a series of changes at WCRS&Co. In October the agency promoted managing director Penny Herriman to chief executive, and merged with its sister digital shop Altogether.
WCRS&Co will now embark on a hunt for a new creative director. Herriman said: "Renewed creativity lies at the heart of the future of the new WCRS&Co and that’s why we’ll be looking to hire the very best talent in the market."
Leon Jaume, the executive creative director at WCRS&Co's parent Engine Group, said: "Yan and Luke have helped me build a great department that has produced some outstanding work and now feel they are ready for fresh challenges. They are good friends of the agency and we thank them for their contribution and wish them well for the future."