Background: Evidence-based interventions often develop strategies to engage diverse populations while also attempting to maintain external validity. When using health IT tools to deliver patient-centered health messages, systems-level requirements are often at odds with ‘on-the ground’ tailoring approaches employed in patient-centered care, particularly regarding ensuring equity is achieved linguistically diverse populations. Methods: STAR MAMA, is a 5-month bilingual (English and Spanish) intervention adapted from the Diabetes Prevention Program, examined in a pilot RCT conducted among 181 post-partum women with recent gestational diabetes. Fidelity to pre-determined ‘core’ intervention components (e.g. systems integration) as well as important ‘modifiable’ components focused on population equity (e.g. health coaching responsiveness, and variation in outcomes by language), were assessed, using an adapted implementation fidelity framework. Evaluation data included participant-level surveys, systems-level databases of message delivery, call completion, and health coaching notes.Results: Participant mean age was 31.5 years, 96.6% of participants are Latina and 80.9% were born outside the US. Among those receiving the STAR MAMA calls 55 received the calls in Spanish (61%) and 35 English (39%). Of those in the call arm, 81 women (90%) completed all 20 weeks of the program. There were many more systems errors in the beginning of the program, than over time. Health coaching triggers were also more widespread in the first several weeks of the STAR MAMA intervention, notably among Spanish-speakers. Although Spanish speakers had more triggers than English-speakers, the difference was not statistically significant. Of the calls that triggered a health coach follow-up, a call-back attempt was made for 85.4% (n=152) of the English call triggers and for 80.0% (n=279) of the Spanish call triggers (NS). Of those with attempted calls, health coaching calls were complete for 55.6% (n=85) of English-language call triggers and for 56.6% of Spanish-language call triggers (NS). Some differences in acceptability were noted by language, with Spanish-speakers reporting higher satisfaction with prevention content (p=<0.01) and English-speakers reporting health coaches were less considerate of their time (p=0.03). Conclusions: Implementation fidelity for health IT interventions involving health coaching should address moderating factors, such as language, as well as systems level factors.Trial Registration: National Clinical Trials registration number: CT02240420 Registered September 15, 2014 . ClinicalTrials.gov