WPP's third-quarter revenue rose 3.1 percent to $4.41 billion, according to the company's trading report.
The results were lower than expected for the British multinational advertising and PR giant. WPP blamed a strong U.K. pound and weak currencies in faster-growth markets for dragging down the figures.
In constant currency terms, revenue was up 10.6 percent, while like-for-like revenue was up 7.6 percent.
The U.K. was the strongest-performing region in terms of constant currency revenue growth, at nearly 15 percent. North America and Western Continental Europe dipped 0.3 percent and 2.5 percent respectively.
Like-for-like net sales for the third quarter rose 3 percent to $3.8 billion. This represents a slowdown as sales were up 4.1 percent in the first half of the 2013-14 financial year.
WPP said it still leads the pack in new business. It reported $1.7 billion in new business in the third quarter, which includes all losses. Its Ogilvy & Mather, JWT, Y&R and Grey units generated combined new-business billings of $276.2 million.
WPP stated that it expects fourth-quarter revenue and net sales to rise slower than they did in the first nine months of the year, blaming sales across North America, Continental Europe and Latin America.
Despite this, it reiterated its full-year target of keeping like-for-like net sales growth at more than 3 percent and operating margin to net sales improvement of 0.3 margin points on a constant currency basis.