<p>Older adults are often underdiagnosed and undertreated for substance use disorders due to difficulty recognizing signs of substance use disorders in this population, as well as difficulty applying the DSM criteria to older adults. The current paper focuses on the prevalence of alcohol and cannabis use among older adults, as well as best practices for assessment and intervention. Through the integration of a case presentation, the current paper highlights common signs of substance use among older adults, clinical and ethical challenges in substance use disorder diagnosis and treatment among older adults, appropriate substance use assessments for older adults, and a variety of evidence-based treatment approaches that can be used with this population.</p>