The Soho-based agency, founded by former Publicis Dialog director Steven Cooper, offers services from corporate identity and brand design, to web development and advertising.
RedRoute's clients include The Brand Cellar, Radio Centre, Hewlett Packard and Savills International. As chairman, Smith will be involved in helping the agency expand over the next five years and aid the development of its own brand.
Cooper said: "Breathing new life into older, established brands can be far more profitable for a company than inventing something new from scratch – especially given current financial constraints.
"We want to further develop our techniques for achieving these results and we’re delighted that Martin, who has worked with so many great brands at great agencies, is bringing his knowledge and experience to help us develop our own brand for the future."
Smith said: "Many great brands have been allowed to slip from public consciousness, but in these recessionary times, marketers are recognising the benefit of capitalising on the latent equity and goodwill in these brands. In its first five years, RedRoute has had a superb record of achieving this with style and commercial success."
Eighteen years after co-founding BBH, Smith joined Grey as CEO in 2000, but left after a year, following a fallout with the agency.
In 2007, he became head of public affairs at The Institute of Cancer Research and, since 2010, has been working across a portfolio of companies in areas as diverse as renewable energy, brand communication, social network marketing, and recruitment.