The account is worth approximately £4m in the UK and will encompass TV, print and digital planning and buying. The pitch took place in Paris against OMD. The last agency of record in the UK was Manning Gottlieb OMD.
A TV campaign is expected to break in late spring.
Sagem specialises in the production of electrical goods such as mobile phones, modems, optical cables and video projectors.
The company's latest project came out of a $50m (£31.9m) contract with the government of the United Arab Emirates. Sagem will work with the country's Ministry of Interior in managing and designing a system that will oversee the production and issue of several million electronic identity cards for citizens.
The win is an early boon for ZenithOptimedia UK's new management team of Antony Young and Greg Turzynski. Young joined the agency as the chief executive in January this year following the UK merger between Zenith Media and Optimedia. He previously worked at the agency's Asia-Pacific outfit.
Turzynski was given sole responsibility for the day-to-day running of the agency last month when his fellow joint managing director, Tim Greatrex, resigned.
The agency then promoted the former managing partners Gerry Boyle, Mark Waugh and Tom George to be Turzynski's deputy managing directors.
The agency's new business, brand development and the expansion of Alliance, its sponsorship consultancy, will be overseen by its newly promoted commercial director, Greg Grimmer.
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