10055 Background: As patients with cancer are increasingly prescribed oral chemotherapy, they share greater responsibility for ensuring adherence and monitoring side effects. The aim of this study was to test the effect of a smartphone mobile app to improve adherence and symptom management in patients prescribed oral chemotherapy. Methods: From 2/15 to 12/16, 181 patients with diverse cancers prescribed oral chemotherapy were randomized to receive either the smartphone mobile app or standard care. The mobile app included a medication treatment plan with alerts, symptom reporting module, education library, and cancer-specific resources. The primary outcome was adherence, measured by electronic pill cap (MEMS) and self-report (Morisky Medication Adherence Scale; MMAS). To assess symptoms, mood, and satisfaction with care, participants completed the MD Anderson Symptom Inventory, Hospital Anxiety & Depression Scale (HADS); and Functional Assessment of Chronic Illness Therapy-Treatment Satisfaction (FACIT-TS) at baseline and 12 weeks. General linear models were used to assess intervention effects on patient outcomes. Results: Study groups did not differ across outcome measures from baseline to week 12. Secondary analyses showed that baseline adherence (MMAS) and anxiety (HADS) were moderators of intervention effects on adherence and treatment satisfaction. Among patients who reported adherence problems, those assigned to the mobile app had better average MEMS adherence (Mean Diff = 19.30, 95% CI = 0.09-38.51, p = .05) and satisfaction with clinician explanations per the FACIT-TS (Mean Diff = 1.69, 95% CI = 0.25-3.13, p = .02) compared to standard care. Also, among patients with higher anxiety, those in the mobile app group reported better adherence on the 12-week MMAS (95.2% vs. 68.0%, OR = 0.11, 95% CI = 0.01, 0.94, p = .04) and satisfaction with interpersonal treatment per the FACIT-TS (Mean Diff = 0.76, 95% CI = 0.13-1.39, p = .02) compared to standard care. Conclusions: Although potentially not for everyone taking oral chemotherapy, a smartphone mobile app to improve adherence and treatment satisfaction may be useful for patients with certain risk factors, such as those struggling with adherence or anxiety. Clinical trial information: NCT02157519.