Allen, 78, is not attending the ceremony and Hollywood Foreign Press Association made the decision to honour Allen knowing that the filmmaker would not come, reported Deadline.
Keaton, 67, was then approached about receiving the award on his behalf.
Keaton and Allen met in 1968 when she auditioned and was cast in his Broadway play, 'Play It Again, Sam'. They were in a relationship for sometime and are still good friends.
Allen is not known to attend award ceremonies and was not even present to receive any of his four Oscars out of 23 nominations. He has also given Golden Globes a miss despite 13 nominations and two wins.
He did attend the 2002 Academy Awards but as an ambassador of New York, thanking Hollywood for its support of his beloved city post-9/11.