Revenues increased to 1.348 billion pounds (1.977 billion euros, 2.405 billion dollars) for the three months to September 30, compared with 1.067 billion pounds in the same period in 2004, boosted by the acquisition of US rival Grey Global.
"Prospects for improvements in trading performance remain good," the company said in a statement accompanying the trading update.
The advertising group also upgraded its 2005 organic turnover growth target to 4-5 percent, compared with previous 3-4 percent range, adding it remained "on track" to meet its 13.7-percent operating margin target for the year.
On a like-for-like basis, which excludes the impact of acquisitions and currency fluctuations, WPP revenue growth was up almost 5 percent on the previous year.
Looking ahead to 2006, the group predicted above-trend growth.
"If industry growth rates this year are 2.0-3.0 percent, next year will probably be at 3.0-4.0 percent, a slight increase in the growth rate," WPP said.
That reflected a significant increase in advertising budgets for the Football World Cup in Germany, the Winter Olympics in Turin and mid-term Congressional elections in the United States.
The group said it had won new business totalling 597 million pounds in the third quarter.
However in recent weeks, WPP has lost out to French rival Publicis for key contracts with US giant Gillette and South Korean electronics group Samsung.
Revenues in North America were up over 26 percent over the quarter, with sales from its British operations rising by almost 10 percent. Continental European revenues were almost 25 percent higher than during the same period last year, while Asia Pacific, Latin America, Africa and the Middle East saw joint turnover jump by over 25 percent.