Introduction: Recent literature emphasizes how over-prescription and lack of guidelines contribute to wide variation in opioid prescribing practices and opioid-related harms. We conducted a prospective, observational study to evaluate opioid prescriptions among uro-oncologic patients discharged following elective in-patient surgery. Methods: Patients who underwent four surgeries were included: open retropubic radical prostatectomy, robot-assisted radical prostatectomy, laparoscopic radical nephrectomy, and laparoscopic partial nephrectomy. The primary outcome was the dose of opioids used after discharge (in oral morphine equivalents [MEq]). Secondary outcomes included: opioid requirements for 80% of the patients, management of unused opioids, opioid use three months postoperative, opioid prescription refills, and guidance about opioid disposal. Results: Sixty patients were included for analysis. Patients used a mean of 30 MEq (95% confidence interval 17.8–42.2) at home and 80% of the patients used 50 MEq or less. A mean of 40.4 MEq per patient was over-prescribed. Fifty percent of the patients kept the remaining opioids at home, with only 20.0% returning them to their pharmacy. After three months, 5.0% of the patients were using opioids at least occasionally. Three patients needed a new opioid prescription. Forty percent reported having received information regarding management of unused opioids. Conclusions: We found 60% of opioids prescribed were unused, with half of our patients keeping these unused tablets at home. Our results suggest appropriate opioid prescription amounts needed for urological cancer surgery, with 80% of the patients using 50 MEq or less of morphine equivalents.