Sisom is an interactive tool designed to help children communicate their cancer symptoms. Important design issues relevant to other cancer populations remain unexplored. This single-site, descriptive, qualitative study was conducted to linguistically validate Sisom with a group of French-speaking children with cancer, their parents, and health care professionals. The linguistic validation process included 6 steps: (1) forward translation, (2) backward translation, (3) patient testing, (4) production of a Sisom French version, (5) patient testing this version, and (6) production of the final Sisom French prototype. Five health care professionals and 10 children and their parents participated in the study. Health care professionals oversaw the translation process providing clinically meaningful suggestions. Two rounds of patient testing, which included parental participation, resulted in the following themes: (1) comprehension, (2) suggestions for improving the translations, (3) usability, (4) parental engagement, and (5) overall impression. Overall, Sisom was well received by participants who were forthcoming with input and suggestions for improving the French translations. Our proposed methodology may be replicated for the linguistic validation of other e-health tools.