Evidence suggests that older adults with mild cognitive impairment (MCI) might not receive evidence-based treatments. We explored the impact of patient MCI on physician decision-making and recommendations for acute ischemic stroke (AIS) and acute myocardial infarction (AMI) in a pilot concurrent mixed-methods study of physicians recruited from one academic center. The mailed survey included a clinical vignette of AIS or AMI where the patient cognitive status was randomized (normal cognition, MCI, or early-stage dementia). The primary outcome was a composite summary measure of the proportion of guideline-concordant treatments recommended. Linear regression compared the primary outcome across patient cognition groups adjusting for physician characteristics. Semi-structured interviews done with 18 physicians (4 cardiologists, 9 neurologists, 5 internists) using a standard guide. Survey response rate was 72% (82/114) (49/61 neurologists; 33/53 cardiologists). As patient cognition worsened, neurologists recommended less guideline-concordant treatments after AIS (Ptrend