Hillman was headhunted for the role a number of months ago.
The Gates Foundation was set up by Bill and Melinda Gates to improve healthcare and reduce extreme poverty globally, while expanding educational opportunities and access to information technology in America.
Hillman said: ‘It’s hard to be taken away from the BBC but the foundation is a great organisation doing some amazing things. The comms role is trying to do a big push on raising the foundation’s profile on issues such as global development and health in Europe and the G20 countries. It’s a huge challenge.’
Hillman said that his priority will be to make sure that the foundation is ‘telling a consistent global story working across a huge number of countries’, adding that social media will play a large part in that operation.
He will report to the foundation’s chief comms officer Kate James.