BackgroundClinical experience in dementia indicates high risk for financial mismanagement, with grave consequences for patients and families. However, to date there has been little scientific study of real world financial errors in dementia or differential vulnerability in different syndromes.MethodCaregivers for people with Alzheimer’s disease (n = 50), behavioral variant frontotemporal dementia (bvFTD, n = 58), and primary progressive aphasia (PPA, n = 39) reported whether care recipients had made financial mistakes within the last year; and if so, categorized these as resulting from: (a) being too trusting or gullible, (b) being wasteful or careless with money, or (c) trouble with memory. In a pre‐registered analysis (https://archive.org/details/osf-registrations-vupj7-v1), we examined two hypotheses regarding vulnerability in different syndromes. Hypothesis 1: Financial mistakes due to being too trusting or gullible and being wasteful or careless with money are more prevalent in bvFTD than in Alzheimer’s disease. Hypothesis 2: Financial mistakes due to trouble with memory are more prevalent in Alzheimer’s disease than in bvFTD.Result32% of Alzheimer’s disease caregivers, 51.7% of bvFTD caregivers, and 30.7% of PPA caregivers reported financial errors in the last year. Concordant with our Hypothesis 1, people with bvFTD were more likely than those with Alzheimer’s disease to make mistakes referable to being too trusting or gullible (OR 4.90, 95% CI 1.55‐19.2, p = 0.012) and to being wasteful or careless (OR 4.41, 95% CI 1.55‐14.7, p = 0.009) in analyses corrected for age, gender, and education. Contrary to Hypothesis 2, people with bvFTD and with Alzheimer’s disease were nearly equally likely to make financial mistakes due problems with memory (bvFTD OR 1.05, 95% CI 0.43‐2.59, p>0.9). In a planned exploratory analysis, no significant differences were found between Alzheimer’s disease and PPA.ConclusionOur positive findings for Hypothesis 1 are concordant with other studies demonstrating socioemotional impairment and insensitivity to adverse outcomes in bvFTD. Meanwhile, our negative finding for Hypothesis 2 may cohere with other work indicating comparable memory impairment in bvFTD and Alzheimer’s disease. More broadly, our findings indicate that caregiver reports can distinguish mechanisms underlying financial mismanagement across different syndromes.