The agency will manage a PR campaign to target both commercial and consumer audiences in five key European territories: UK, France, Germany, Spain and Italy.
The firm is part of ACE Group, a Bermuda and Switzerland-based global insurance and reinsurance firm.
ACE's traditional strength is in the insurance underwriting market, but it also offers insurance products covering property and life, accident and health, reinsurance and travel.
Grayling will look to raise awareness of ACE in Europe among clients and brokers and increase knowledge of ACE as a global insurer.
The agency has also been charged with building understanding of ACE's breadth of services and products.
Grayling won the account following a five-way pitch. The firm has previously used Concise Public Relations to support comms in the UK and Ireland.
The account will be led by Grayling's corporate & financial practice, based in London, working alongside its offices in Paris, Frankfurt, Madrid and Milan.
Jonathan Shillington, MD of Grayling corporate & financial in the UK, said that ACE was 'one of the few truly global insurers'.
He added: 'We want to further strengthen ACE's profile as an insurance leader, by providing a seamless multinational service that highlights ACE's genuine customer-focused approach and fresh perspectives on risk.'
Miles Russell, European comms director for ACE European Group, commented: 'Grayling's on-the-ground knowledge will prove invaluable in assisting the continuing expansion of the ACE brand in each of our core markets.'