Cognitive loss and associated functional decline can reflect many different physiological processes, some of which are progressive and neurodegenerative, others stable or even reversible. Behavior analysts, through their measurement-based practice, are uniquely positioned to detect fluctuations in proficiencies and skill levels that are potentially indicative of decline, and to implement assessment and intervention. The goals of this tutorial are twofold: (1) to provide an overview of neurocognitive disorders, such as those from Alzheimer’s, Lewy body disease, or stroke, and prominent risk factors, such as age and an already compromised nervous system due to prior traumatic brain injury, chronic disease, lifestyle factors, or particular preexisting neurodevelopmental disorders; and (2) to offer a practical step-by-step guide to ruling out reversible conditions, ascertain the appropriate level of social and physical support, and address potential behavioral and emotional changes. Video and audio examples will be provided for training purposes, to illustrate the heterogeneity of individuals’ reactions to functional decline, the difficulties of family members to follow behavioral plans or adapt to their loved one’s loss of skills or repertoires, and the need for medical care navigation. The tutorial will introduce cognitive loss and functional decline as a high-need specialty practice area, amenable to workforce development in behavior analysis.