Dame Helen Mirren has already started filming the project, in which she stars as Maria Altmann, who spent four decades battling Austrian officials for the safe return of art stolen from her family by the Nazis during World War Ii. The stash, including Gustav Klimt's famous The Lady in Gold painting, was returned in 2006.
Reynolds will portray Altmann's young lawyer, Randy Schoenberg, and now Holmes has been added to the line-up as his wife.
Director Simon Curtis has also found a role for his real-life spouse, Downton Abbey star Elizabeth MCGovern, in the movie, alongside fellow new additions Max Irons, Daniel Bruhl and Game of Thrones actor Charles Dance.
Production on Woman in Gold began last week (ends23May14) in the U.K., Austria and the U.S.