Watson joins the firm's board, reporting to global chief executive Tim Bird. He will be based in the agency's London office, and is charged with building global creative capabilities and growing the London-based creative team.
Watson replaces Dick Dunford, who has rejoined TBWA\WorldHealth as executive creative director at the agency's London operation.
Watson joins Health Unlimited from Darkside Communications, where he has been a freelance consultant. Before that, between 2010 and 2014, he was group creative director at Ogilvy Healthworld. He has also worked as executive creative director at Publicis LifeBrands and in the same role at Sudler & Hennessey. He started his career at WCRS/dma, working with the agency's FMCG brands.
Health Unlimited is part of digital and technology marketing services group Unlimited Group, which itself recently made a senior appointment in the guise of Sarah Shilling as group CMO and Michael Richards as group managing director.
Bird said: "Jon is a well-known senior creative talent in our industry. We are delighted to welcome him and his enormous talent to our global team that is working collaboratively as one team to inspire and create imaginative solutions to solving complex health challenges."
Earlier this month, Unlimited Group, which also owns Nelson Bostock and Fever, reported profits before interest and tax of £10.2m, up 17 per cent in its first full financial year since becoming a private company in 2016.