Objective: To determine whether mild cognitive impairment is associated with treatment preferences for the care of serious illness. Design: Observational, cross-sectional study using 2018 Health and Retirement Study data. Participants: 1,334 respondents including 209 respondents whose cognitive function was consistent with cognitive impairment, not dementia (CIND, or mild cognitive impairment) and 1,125 with normal cognition. Main outcomes and measures: Self-reported treatment preferences for life-extending, limited, and comfort care options in two clinical scenarios. One scenario represents a hypothetical patient in good physical health, but with severe cognitive impairment consistent with dementia, and the second represents a patient with physical impairment due to a heart attack, but normal cognitive function. We included measures indicating whether the respondent specified a treatment preference or was unsure, and if they would want or not want the treatment option. Linear probability models were used to compare preferences of those with and without CIND. Results: Respondents with mild cognitive impairment were more likely to report that they were unsure about treatment options across both clinical scenarios. For the limited treatment option, CIND was associated with a lower rate of identifying a treatment option by 7.4 (p=0.060) and 8.3 (0.036) percentage points for the dementia and heart attack scenario, respectively. Among those who articulated preferences, CIND was associated with a marginally higher rate of preference for life-extending treatment in both the dementia (28.5% vs 20.2%, p=0.082) and heart attack scenarios (28.6 vs 20.3, p=0.063). Conclusion and relevance: Cognitive Impairment without Dementia was associated with greater uncertainty about treatment preferences and higher rates of aggressive care preferences among those who specified preferences. Further research should assess whether preferences for aggressive care become more common as cognition declines in order to improve preference-concordant care delivery for patients with cognitive impairment.