Health information technology (IT) tools are increasingly used to improve patient care. However, implementation of English-only health IT tools could potentially worsen health disparities for non-English speakers. We aim to describe the “trans-creation” process of developing linguistically and culturally appropriate health IT tools through a detailed case analysis of a waiting room health mobile app designed to help Spanish-speaking Latino people prepare for primary care visits. We adapted the English-language Visit Planner mobile app for Spanish-speaking Latino patients. We applied culturally defined themes derived from prior published research and input by both skilled linguists and potential end users. Initial changes were iteratively reviewed and edited by a team of writers, health care educators, subject matter experts, patients, and providers. The trans-creation process resulted in the following key culturally mediated changes to the tool: replacing the “provider” actors with “patient” actors; changing the choice of “Stress at Home or Work” (represented by an icon of a house) to “Mi Familia” (translation: my family; icon is an outline of family members holding hands); replacing the English terms “anxiety” and “depression” with “Me siento desanimado”(translation: I am feeling down) to avoid mental health stigma; and using more concise text translation to ensure the wording fit the available on-screen space. The trans-creation process of cultural and linguistic adaptation led to several design changes that would not have been implemented if we had simply translated the words from English to Spanish.