The group's upbeat set of results dispelled concerns about the impact of a soft US economy on the sector.
Omnicom's advertising agencies include BBDO Worldwide and DDB Worldwide. Its biggest clients include Anheuser-Busch and McDonald's. It is led by president and chief executive John Wren.
Omnicom benefited from strong growth in international revenue, which rose 18.3% to $1.53bn compared to $1.3bn a year earlier. Domestic revenue increased 7.6% to $1.66bn.
The US, however, still accounts for the largest proportion of the company's revenue, at about 52%.
Overall organic revenue, a closely watched industry benchmark that excludes foreign currency impact and recent acquisitions, rose 6.4%.
Earlier this year, Omnicom said that it hasn't seen any signs of cuts to marketing budgets; its trading during the first three months of the year is evidence of this assessment.
The group's share price has climbed 3.4% to $47.76 after the results in trading on Wall Street this morning.