Cognitive impairments can increase significantly a person’s level of risk for becoming or remaining homeless. Five topics are explored that address these impairments in preventing homelessness: (1) the nature and estimated prevalence of cognitive impairments among people who are homeless, especially those with vulnerabilities like mental illness or substance abuse; (2) the multiple origins of these impairments; (3) how these impairments impact services for people at risk for homelessness; (4) good practice approaches to handling cognitive impairments in homeless shelters, supported housing programs, and other service systems for people at risk for homelessness; and, (5) important research and practice issues requiring further action.