First-half revenues rose by 1.3% to €729m(£489m), dampened by the appreciation of the Euro against the dollar in the first half of 2007, the group said in it latest quarterly report.
Meanwhile, organic growth was 5.4% in the second quarter and 3.2% in the first quarter, averaging 4.4% across the first six months of 2007.
This was the first time in six years that quarterly growth exceeded 5%.
Havas also reported an increase in net new business wins to €1.2bn(£806m) for the first half, a jump of 38%. Second-quarter new business was up by 44% to €697m(£468m).
The French group, which owns MPG and Euro RSCG Worldwide, attributed the strong organic growth to a number of high-profile account wins last year including Reckitt Benckiser, Sanofi-Aventis, Pfizer, Exxon Mobil, Progressive Direct, SFR, Banco Santander, GSK and Barclays.
Havas also benefited from strong growth in the media and healthcare sectors.
By region, the UK posted a 3.4% rise in second-quarter organic growth and 1.7% growth in the first half, after a steady performance from Euro RSCG in addition to growth in press relations, financial communication and marketing services sectors.
France saw a 2.4% rise in organic growth in the first half of 2007, slightly down on 2.6% growth in the first half of 2006.
The rest of Europe, excluding France and the UK, saw second-quarter revenue growth of 9.1% and first-half growth of 8.7%, up from 8.2% in 2006. Havas enjoyed double-digit growth in Ireland, Belgium and Denmark.
North America saw a return to orrganic growth of 4% in the second quarter, due mainly to the "landmark" Sears account win. First-half organic growth came in at 1.6% this year, up from a 5.3% decline in 2006.
In Latin America, growth in advertising and media consulting helped propel Havas to 16.8% growth in the first half of 2007, up from 16.5% in 2006.
Finally, the Asia Pacific region continues to see "dynamic growth", 9.7% in the first half compared to a 4.8% decline in the first-half of 2006, boosted by the Dell account win.