The Sherlock Holmes star plays Assange in the movie The Fifth Estate, which has just begun filming.
Cumberbatch, below, stars alongside Daniel Bruhl, who portrays Daniel Domscheit-Berg, one of Assange's early supporters.
The film is based on two books about the rise of Assange, who is holed up in Ecuador's London embassy after being given asylum. The Australian faces extradition to Sweden over sexual assault claims.
Director Bill Condon said: "We want to explore the challenges of transparency in the information age and, we hope, enliven and enrich the conversations WikiLeaks has already provoked."