The agency won a pitch process to handle work at group level for the company, which is owned by the Duke of Westminster, Gerald Grosvenor, and his family.
Headland’s role will combine corporate reputation management, financial communications, media relations support and campaign management.
The group has around £5.8bn in property assets, with a major presence in London that include estates in Mayfair and Belgravia.
Last year it sold off a number of its luxury London assets amid fears that the property market was overheating, switching focus to more mid-market housing in the process.
However, Grosvenor’s group director of comms Fennella Gentleman emphasised that the agency would not be handling day-to-day comms around property portfolios but instead broader strategic positioning of the group as a whole.
A key aspect of this, she said, was to rebalance the image of the group in line with its international presence, which includes offices in 18 cities across the globe.
Stating that the business had nearly reached a point where 50 per cent was based outside of the UK, she said: "We are not after more coverage, the point is whether the coverage reflects what we’re trying to do, and we’re keen to emphasise the international aspect of the group."
Another focus for the agency would be on portraying Grosvenor as more than just a property owner, added Gentleman.
"It’s not just a matter of owning bricks and mortar. We’re about skillsets, and we know how cities tick in terms of what kind of property and public spaces are needed to help create and manage vibrant cities. There’s a broader social conscience."
The agency was hired by Grosvenor after seven years with Quiller Consultants, which Gentleman praised for a "successful relationship".
Neil Hedges, partner at Headland and lead adviser to Grosvenor, said the brief was "right in the heart of two of our biggest sectors: property and financial services".
"Grosvenor’s rich history is only matched by its commitment to the long term, something that particularly chimes with the Headland team," he added.
Gerald Grosvenor, whose family have owned property in London since the 17th century, was rated as the third richest British citizen by this year's Sunday Times Rich List with a personal value of £8.5bn.
Quiller declined to comment.