Background <p>Approximately 68&#xa0;million people in the U.S. speak a language other than English at home. Multilingual families face many barriers to accessing mental health care, including language and cultural differences. Digital low-intensity treatments (D-LITs) can potentially address these barriers by providing accessible, scalable interventions. However, D-LITs must be modified to account for the daily, real-world complexities of youth and implementation contexts. The current case study aimed to systematically describe modifications, informed by feedback from key players, to a monolingual D-LIT to increase access to evidence-based interventions for multilingual families (i.e., Spanish/English).</p> Methods <p>The Teen Assess, Check, and Heal (TeACH) System is a D-LIT for teens with anxiety implemented via a randomized controlled trial across multiple pediatric primary care clinics serving patients in Chicago, Illinois, USA. By evaluating participant-facing materials and recruitment procedures during the design and implementation stages, we engaged in an iterative refinement process to improve the TeACH System to better serve youth with Spanish-speaking caregivers. Modifications were retroactively coded to document their context and purpose using the FRAME-IS, a framework for documenting modifications to the implementation strategies of evidence-based interventions.</p> Results <p>Forty-two percent (155/366) of the teens who assented opted to include parental permission, and 14.6% indicated that Spanish was their guardian’s preferred language. Six key modifications aimed to (1) increase health equity through culturally-appropriate content; (2) improve fidelity to IRB consent procedures when engaging with Spanish-speaking caregivers; (3) increase reach of the TeACH System; and (4) improve feasibility of recruitment in primary care settings. Most of the modifications occurred during the implementation phase (83%) and were unplanned/reactive (66%). Recruitment staff led most (83%) of the decision-making regarding modifications. All modifications were applied across the intervention to improve TeACH’s ability to better serve multilingual families.</p> Conclusion <p>Culturally-responsive modifications must be made at all stages of design and dissemination to ensure that research participation is equitable, even when an intervention is intended to be delivered in English. Culturally adapted and appropriate D-LITs may serve as a catalyst for enhancing the accessibility and utilization of effective digital tools to address mental health disparities experienced by multilingual families.</p> Clinical trial number <p>Not applicable.</p>