The pair were spotted on location in San Francisco shooting the TV project as the film's title characters.
The couple certainly looked the part with Clive, 46, wearing Ernest Hemingway's signature beret and round metal framed glasses and Nicole, 43, sporting tousled hair and wide-legged trousers.
The film tells the story of the writer and his second of four wives.
Their tumultuous relationship and five-year marriage began when they met at a local Key West bar in 1936.
They married in 1940 after romancing in Europe while Hemingway wrote his famous novel For Whom The Bell Tolls for which she was the inspiration.
Due to their busy careers - Martha was a World War II correspondent - the couple spent extended periods of time apart and they ended up getting divorced in 1945.
Years later, both tragically ended their own lives - Hemingway in 1961, after struggling with psychological issues and Gellhorn years later in 1998 after a cancer battle and losing her sight.
The all star cast also includes David Strathairn, Parker Posey, Rodrigo Santoro, Molly Parker, Santiago Cabrera, Peter Coyote, Saverio Guerra, Diane Baker, Tony Shalhoub and Lars Ulrich.
The film is shooting in Northern California over the next month and will air on HBO in the U.S next year.