On Secret Service is a 1933 British thriller film directed by Arthur B. Woods and starring Greta Nissen, Karl Ludwig Diehl, Don Alvarado, and Austin Trevor. It was produced by British International Pictures. It is based on the 1933 German film Spies at Work with Karl Ludwig Diehl repeating his role from that film. On Secret Service premiered in London on 15 December 1933 and was theatrically released on 21 May 1934. In the United States, the film was released on 9 February 1936 as Spy 77.The film was shot at Elstree Studios with sets designed by the art director Duncan Sutherland.