Diane Keaton Amy Sussman/Getty Images Share on Facebook Share on X Share to Flipboard Send an Email Show additional share options Share on LinkedIn Share on Pinterest Share on Reddit Share on Tumblr Share on Whats App Print the Article Post a Comment Diane Keaton's cause of death has been revealed days after the Hollywood icon died at age 79. The Oscar winner's family told People magazine that she died from pneumonia on Oct. 11.