Emily Gameiro who plays the role of Marion is non else than the director Jonathan Kingston Gameiro's sister. True Heart was their first collaboration in the film industry. Their mother, father and grand mother also worked on True Heart during the production of the movie.
During the execution scene a close-up can be noticed on a french resistance soldier. It is Renan Robillard the producer of True Heart dressed up as french resistant.
The castle where most of the interior scenes were shot was a location where many German soldiers used as a hiding place during the second world war in France.
The FFI soldier who hands the picture to the Officer Robert Ferrier played by Daniel Quilez is his son Romain Quilez.
"True Heart" was originally a non permanent production name. After the production ended, the producers decided to keep the title "True Heart" as they considered it was a suitable title, and also reflected the atmosphere and energy shared on set by the cast and crew.