BACKGROUND AND OBJECTIVES: Informal care is the primary source of support for older adults with cognitive impairment, yet is less available to those who live alone. We examined trends in the prevalence of physical disability and social support among older adults with cognitive impairment living alone in the United States. RESEARCH DESIGN AND METHODS: We analyzed 10 waves of data from the U.S. Health and Retirement Survey spanning 2000-2018. Eligible people were those aged ≥65, having cognitive impairment, and living alone. Physical disability and social support were measured via basic and instrumental activities of daily living (BADLs, IADLs). We estimated linear temporal trends for binary/integer outcomes via logistic/Poisson regression, respectively. RESULTS: A total of 20 070 participants were included. Among those reporting BADL/IADL disability, the proportion unsupported for BADLs decreased significantly over time (odds ratio [OR] 0.98, 95% confidence interval [CI] 0.97-0.99), and the proportion unsupported for IADLs increased (OR = 1.02, CI 1.01-1.04). Among those receiving IADL support, the number of unmet IADL support needs increased significantly over time (relative risk [RR] 1.04, CI 1.03-1.05). No gender disparities were found for these trends. Over time, Black respondents had a relatively increasing trend of being BADL-unsupported (OR = 1.03, CI 1.0-1.05) and Hispanic and Black respondents had a relatively increasing trend in the number of unmet BADL needs (RR = 1.02, CI 1.00-1.03; RR = 1.01, CI 1.00-1.02, respectively), compared to the corresponding trends in White respondents. DISCUSSION AND IMPLICATIONS: Among lone-dwelling U.S. older adults with cognitive impairment, fewer people received IADL support over time, and the extent of unmet IADL support needs increased. Racial/ethnic disparities were seen both in the prevalence of reported BADL/IADL disability and unmet BADL/IADL support needs; some but not all were compatible with a reduction in disparity over time. This evidence could prompt interventions to reduce disparities and unmet support needs.