It is the world's largest advertising agency by revenue (as of 2019) and one of the "Big Four" along with Publicis, Interpublic Group of Companies and Omnicom.

WPP plc owns many companies, which includes advertising, public relations, media, and market research networks such as AKQA, BCW, CMI Media Group, Essence Global, Finsbury, Grey, Hill+Knowlton Strategies, Mindshare, Ogilvy, Wavemaker, Wunderman Thompson, and VMLY&R.

The company’s milestones:

- In 1971: The company was founded as Wire and Plastic Products plc to manufacture wire shopping baskets.

- In 1986: WPP became the parent company of Picquotware, a manufacturer of teapots and jugs, based in Northampton.

- In 1987: WPP acquired Scott Stern Associates - Scotland's largest advertising and design firm at the time - and J. Walter Thompson (including JWT, Hill & Knowlton, and MRB Group).

- In 1988: The company listed on the NASDAQ.

- Năm 1989: WPP acquired Ogilvy Group.

- In 1990s: WPP acquires firms in the healthcare advertising, digital-marketing, online shopping, digital media, data management, retail and corporate consultancy, and sports-marketing industries.

- In 1998: WPP formed an alliance with Asatsu-DK Inc. of Japan.

 - May 2000: WPP agreed to acquire the United States-based Young & Rubicam Group for $5.7 billion, in what was at the time the largest ever takeover in the advertising sector.

- In 2007: WPP Digital was created to develop the group's digital capabilities.

- In 2008: WPP acquired market research firm Taylor Nelson Sofres for £1.6 billion.

- In 2012: WPP agreed to acquire the digital advertising agency AKQA for US$540 million.