Sheriff, who is overseeing media, strategy and PR, and is reporting to corporate affairs director Clare Harbord, said: "It's a really exciting time to join the team at Heathrow. We have an important agenda to make Heathrow the best passenger airport service in the world as well as be good neighbours to the communities around us.
"Heathrow is a national asset, a major export hub and employer. So there's lots to do and I'm rolling my sleeves up with the team already."
Prior to Diageo she had held a number of jobs in central government comms.
In 2013, she moved from her dual role as official deputy spokeperson for the Prime Minister and head of news at Number 10 to take up the top comms job at the Department for Transport. Previous to this she had worked at the Ministry of Justice.
Sheriff joins the organisation two months after the Airports Commission recommended a third runway be built at what is one the world's busiest airports by passenger numbers. Heathrow faced - and in spite of the recommendations - continues to face stiff opposition to the plan with Gatwick Airport also wanting to expand.
The airport lost its director of PR Simon Baugh earlier this year after he headed to the Department for Transport to take the role previously held by Sheriff. Heathrow also appointed a new consumer PR agency in the summer.