Background: The use of patient reported outcome measures (PROMs) to monitor cancer treatment tolerability has been shown to positively impact outcomes. The purpose of this study was to characterize the incidence and severity of side effects, patient self-management confidence, and medication adherence in patients receiving oral oncolytic therapy. Methods: This multicenter, cross-sectional, observational study was conducted across 6 Michigan oncology practices from July 2016-December 2018. Patients were eligible to complete PROMs during the course of their treatment if they were receiving an oral oncolytic medication (excluding endocrine therapy). Results: There were a total of 2252 PROMs completed in 695 patients. Patients were 48% female, a median age of 69 years, and most commonly receiving treatment with capecitabine (18%), palbociclib (10%), and lenalidomide (9%). 54% of PROMs had at least one Edmonton Symptom Assessment Scale (ESAS) symptom rated as moderate or severe. Patients indicated the presence of a most bothersome symptom (MBS) in 35% of PROMs. Most common MBSs were fatigue (26%), pain (16%), constitutional symptoms other than fatigue (15%), and nausea/vomiting (14%). Non-adherence was reported in 20% of PROMs. ESAS symptoms rated as moderate or severe, the presence of a MBS, and lower confidence scores all correlated with medication non-adherence. Conclusions: Patients taking oral oncolytics for their cancer treatment experience a high symptom burden with more than 50% experiencing a moderate to severe symptom. Optimizing symptom management and providing patient education that increases patient confidence in self-management may improve medication adherence and patient outcomes.