Patients with life-limiting cancers are commonly prescribed opioids to manage pain, dyspnea, and cough. Proper prescription opioid disposal is essential to prevent poisonings and deaths. We examined opioid disposal practices of patients referred to a Canadian outpatient palliative care clinic (OPCC). The primary objective was to determine the prevalence of OPCC patients who did not routinely dispose their opioids. The secondary objectives were to examine their methods of opioid disposal and to identify patient characteristics associated with routine disposal of opioids. This cross-sectional study involved a retrospective chart review of new, adult patients who were seen in a Canadian OPCC (September 2018-August 2019) and completed a survey about opioid-related constructs: source of prescriptions, use, storage, disposal, and knowledge about associated harms. Among the 122 study participants, half (58/111, 52.3%) reported that they did not routinely dispose their opioids. The most common method of disposal was by giving them to pharmacists (69/88, 78.4%). Cannabis use (odds ratio [OR]: 3.7, 95% confidence interval [CI]: 1.1-11.8) and neuropathic medication use (OR: 3.0, 95% CI: 1.2-7.2) were positively associated with routine disposal of opioids. Conversely, reports of an increased amount of opioid use in the past six months were negatively associated with routine disposal of opioids (OR: 0.38, 95% CI: 0.16-0.88). The high prevalence of people with life-limiting illnesses who do not routinely dispose their opioids requires increased attention. Interventions, such as education, are needed to reduce medication waste and opioid-related harms.