Background: Patients prescribed oral anticancer therapy receive less support for adherence and symptom monitoring from oncologists compared to infusional cancer therapy, which can result in lower quality care and worse disease outcomes. Identifying factors related to adherence can guide efforts to develop patient-centered interventions. The goal of this analysis was to examine associations among patients’ illness understanding, information preferences, and oral anticancer therapy adherence. Methods: We conducted a secondary analysis of a randomized trial testing the efficacy of a mobile application to improve assessment of symptoms and treatment adherence. Eligible patients included adults diagnosed with cancer prescribed oral anticancer therapy. To assess adherence, participants stored their medication for three months in a Medication Event Monitoring System (MEMS) bottle that electronically records the date and time the bottle is opened. At baseline, participants completed the Prognosis and Treatment Perceptions Questionnaire, which assesses patients’ illness understanding and information preferences in communicating with oncologists. We conducted linear regression to examine associations among patients’ illness understanding, information preferences, and medication adherence. Results: The study included 181 patients prescribed oral anticancer therapy (Mean age = 53.30 years; 53.6% female; 87.8% white). The most common cancer types were hematologic (33.1%), lung (18.2%), and breast (14.4%) malignancies. Two-thirds (66.9%) were prescribed oral targeted therapies, and 35.5% self-identified as terminally ill. Controlling for intervention effects, patients who reported wanting as many details as possible related to their cancer and treatment had higher MEMS adherence over the three-month study period (B = 12.84, 95%CI: 3.65, 22.03, p =.006) versus those who preferred to know fewer details. Also, patients who reported that it was extremely important for them to know their prognosis had higher adherence (B = 9.93, 95%CI: 1.73, 18.13, p =.018) versus those who rated knowing about prognosis as less important, though this relationship was moderated by illness understanding. Specifically, in the subgroup of patients reporting that they were not terminally ill, the association between wanting to know about prognosis and MEMS adherence remained significant (p =.006), which was not the case for patients identifying as terminally ill (p =.776). Conclusions: In this sample, patients’ desire for information about their cancer and prognosis was strongly associated with higher adherence to oral anticancer therapy over the following three months. Yet, this association may be stronger among those who do not identify as terminally ill. Targeted interventions that support patients who prefer fewer details about their illness and prognosis may improve medication adherence.