Focusing on the pivotal period of 1919–23 and the large-scale humanitarian responses in Central and Eastern Europe, this paper discusses the development of advocacy in the movies made by organizations like the ICRC, Save the Children Fund or American Relief Administration. While aid agencies observed and competed with each other for visibility, humanitarian cinema shaped visual advocacy, grounded in the idea that ‘seeing is believing’. Exploring the fragmented audiovisual archives, as well as magazines and promotional material, this paper explores the testimonial function of humanitarian films in the 1920s. It first shows that the immediacy of the cinema technology increased the immersive and affective experience of the viewers by using forensic evidence and images of the body in pain. It then analyses how these films compelled audiences to witness suffering and act through persuasion, suggestion, and emotions. Finally, it inquires into the use of eyewitness images and first-hand accounts during the screenings, to show how these movies operated within larger regimes of visibility, while making claims on behalf of distant beneficiaries.