Keith Weed worked as an engineer after graduating university before joining Unilever in 1983 as a marketer. Throughout his career at Unilever, he has been chairman of Lever Fabergé and chairman of Unilever Export. He has worked for Unilever in the UK, France, the United States, both in global and regional roles across general management and marketing. More recently he was global head of Home Care & Hygiene. As Unilever's Chief Marketing and Communications Officer, Weed is on Unilever's executive board with the Marketing, Communications and Sustainable Business teams reporting to him.

Since becoming CMCO, Weed has pioneered new ways of integrating sustainability in business and led the creation of a "sustainable living plan", which seeks to grow Unilever while reducing its environmental footprint and increasing its social impact. He also dissolved Unilever's corporate social responsibility department and has integrated sustainable growth throughout Unilever's business. In 2014, Weed gave a TED Talk about the global issue of climate change and argues that sustainability and economic growth can go hand-in-hand.

Weed has also directed significant advances in digital and influencer marketing and technologies within Unilever, championing the 3Vs of Viewability, Verification and Value across the industry. He is committed to tackling stereotypes – gender and beyond – in advertising through Unilever's #Unstereotype initiative and is the architect behind the #Unstereotype Alliance, co-created with UN Women, bringing together 24 companies to remove the portrayal of unhelpful stereotypes from their advertising by 2020.

In 2016 Weed was LinkedIn's second most influential writer on the platform in the UK.

In 2017, he was voted as the Marketers' Marketer of the Year by Campaign readers. He was also voted Global Marketer of the Year 2017 by the World Federation of Advertisers.

Weed was named the World's Most Influential CMO in 2017 and 2018 by Forbes. In 2018 Weed also received The Drum's Lifetime Achievement Award and featured in the Top 50 Financial Times HERoes list as a Champion of Women in Business.

Outside Unilever, Weed is the president of the Advertising Association, a fellow of The Marketing Society, of which he was president from 2003 to 2006, and is a fellow of the Institute of Mechanical Engineers. He was a non-executive director of Sun Products Corporation from 2008 to 2016. He is currently chairman of Business in the Community International, a board of trustees director for Business in the Community, a board director of the Effies and a trustee of Grange Park Opera.

In 2020 Weed was appointed president of the Royal Horticultural Society.