e13659 Background: Secure messaging (SM) enables patients to ask clinicians questions asynchronously. Benefits include enhancing patient engagement, contributing to oral chemotherapy adherence, and lowering symptom distress. However, patients are unsure how to address concerns effectively, and clinicians find it challenging to decipher patients’ needs within messages. Coupled with clinicians not having adequate time to respond to messages, breakdowns in communication are common. We developed an interactive guide to help patients with cancer craft effective secure messages. It featured an oncologist providing strategies to write messages with specificity, expressing concerns, stating needs, being direct, and included a downloadable tip sheet. Methods: Patients 18+ with a current cancer diagnosis who were enrolled in the portal at a large health center were recruited. Between October 2023 and January 2024, participants were sent a link to interact with the guide, followed by a survey. The survey included several measures: 1) Communication and Attitudinal Self-Efficacy scale for cancer (CASE-cancer); 2) Digital Behavior Change Intervention (DBCI) Engagement Scale; 3) Website User Satisfaction questionnaire (WUS); 4) Acceptability of Intervention Measure (AIM); 5) Intervention Appropriateness Measure (IAM). We used R version 4.3.2 for the descriptive analysis. The Wilcoxon rank-sum test compared groups by demographic categories. The local IRB approved this study. Results: One hundred patients participated. Median age was 64 years (range=21-86), 54% male, 83% white, 35% diagnosed with prostate cancer, 35% lung cancer, and 23% hematologic cancer. Respondents reported high levels of self-efficacy based on CASE-cancer (mean 43.3 of 48). Respondents averaged 15 minutes using the guide. 96% thought the guide’s content was presented clearly, 95% found it easy to understand, 90% enjoyed using it, 89% thought the guide was suitable, and 88% could rely on its information. Results by demographic categories found that non-white respondents (M = 43.0) were significantly more engaged than white respondents (M = 28.4), P = 0.038 , and those with a bachelor’s degree+ (M = 96.5) had higher satisfaction than those without (M = 91.6), P = 0.025. Conclusions: Patients with cancer embraced an interactive guide that provided strategies to craft secure messages. They found it engaging, satisfying, acceptable, and appropriate, with racially minoritized patients being most engaged. As SM is a widely used tool for patient-clinician communication, it is crucial to concentrate on the way messages are constructed. We found potential to improve patients’ message-writing techniques, which could result in clinicians writing more complete answers to questions. Additionally, there is the possibility to enhance underserved patients’ communication skills and make them more engaged in their care.