Mr Keene, who has worked for PA for 21 years, is to become a Member of the Royal Victorian Order (MVO).
"I'm absolutely delighted and totally thrilled," he said. The former royal photographer added, "I've had brilliant opportunities at The Press Association to see all the members of the Royal Family carrying out their duties."
His award is in the Queen's personal gift and is bestowed independently of Downing Street.
Mr Keene, 49, began working as a photographer at the Herald Express in Torquay, Devon, in his early 20s, before joining the PA, national news agency, in 1986. He spent nine years as a PA photographer including five years as the agency's royal photographer.
He photographed the Queen on her historic trips to Moscow and South Africa, Diana, Princess of Wales, as she sat alone outside the Taj Mahal, and the Duchess of York trekking to Mount Everest.
He was appointed picture editor in 1995 and group picture editor last year. He led pictorial coverage during momentous events in royal history including the death of Diana and the funeral of the Queen Mother.