Sir Martin Sorrell's business makes 55% of its money from tech, well ahead of any other sector.
Organic revenue fell in every region, including by 9% in Asia Pacific, although performance was ahead of ad spend forecasts.
The social-media company has doubled its user numbers in India, but continues to struggle to monetise its users outside the US and Europe.
The company is looking to become more agile under challenging conditions.
Japan's third-largest advertising agency enters privatisation on a stable footing.
Dentsu's 2017 results and 2018 forecasts show that creating a better place to work is a costly business.
Top news, insights and analysis every weekday
Sign up for Campaign Bulletins