UFA insisted on the film being made inexpensively, as Fritz Lang's previous film Metropolis (1927) had brought the studio to near bankruptcy. Lang therefore chose to do most of the shots in narrow settings with lots of close-ups, as no big sets had to be built up for that way of filming. Fortunately "Spione" became a huge success.
Gerda Maurus, whose film debut this was and who met Fritz Lang for the first time here, later had a long relationship with the director, eventually causing his divorce from Thea von Harbou, who remained his regular co-author up until The Testament of Dr. Mabuse (1933), Lang's last German film before emigrating to the US.
Fritz Lang consciously chose to introduce Willy Fritsch as a scruffy homeless person, for Fritsch was most known from his previous films as the elegant gentleman he later becomes in this movie as well.
At the 1 hour mark, when Sonja has her meeting with Jellusic, several posters for Fritz Lang's, Metropolis (1927) can be seen posted on walls along the street.
Debut of actress Gerda Maurus who got the lead in this film also it was the debut of actress Lien Deyers,
Fritz Lang: [Regulars] Actors Rudolf Klein-Rogge and Fritz Rasp in leading roles, Thea von Harbou co-writing the script.