We built an augmented reality (AR) patient education application for portable iOS and Android devices that allows patients to view a virtual simulation of themselves receiving radiation treatment. We created software that reads data from the clinical treatment planning system and renders the patient’s actual radiotherapy plan in AR on a tablet or smartphone. The patient's CT simulation data are converted into a 3D translucent virtual human shown being treated with visible radiation beams from a virtual linear accelerator. We conducted a patient study to determine if showing patients this AR simulation improves patient understanding of radiotherapy and/or reduces anxiety about treatment. A total of 75 patients completed this study. The most common plans were 3D breast tangents and intensity modulated radiotherapy lung plans. Patients were administered questionnaires both before and after their AR viewing experience. After their AR viewing, 95% of patients indicated that they had a better understanding of how radiotherapy will be used to treat their cancer. Of the 35 patients who expressed anxiety about radiotherapy beforehand, 21 (60%) indicated that they had decreased anxiety after the AR session. In our single-arm prospective patient study, we found that this simplified low-cost tablet-based personalized AR simulation can be a helpful educational tool for cancer patients undergoing radiotherapy.