Objective: Increasing evidence points to mild alterations in everyday functioning early in the course of Alzheimer's disease and related dementias (ADRD), despite prior research suggesting functional declines occur primarily in later stages. However, daily function assessment is typically accomplished with subjective self- or informant-report, which can be prone to error due to various factors. Performance-based functional assessments (PBFAs) allow for objective evaluation of daily function abilities, but little is known on their sensitivity to the earliest ADRD-related brain alterations. We aimed to determine the neural correlates of three different PBFAs in a pilot study. Method: A total of 40 older participants (age = 70.9 ± 6.5 years; education = 17.0 ± 2.6 years; 51.5% female; 10.0% non-White; 67.5% cognitively normal) completed standardized PBFAs related to medication management (MM), finances (FIN), and communication abilities (COM). Participants underwent diffusion tensor imaging (DTI) scans, from which mean fractional anisotropy (FA) composite scores of late- (LMF) and early myelinated (EMF) fibers were calculated. Linear regression analyses controlling for age and global cognition were used to assess the relationship of PBFAs with FA. Results: Better performance on MM was associated with higher mean FA on LMF composite (t38 = 2.231, p = .032), while FIN and COM were not (ps > .05). PBFAs were not associated with EMF (p > .05). Conclusions: Our preliminary findings demonstrate better performance on a PBFA of medication management is associated with higher FA in late-myelinated white matter tracts. Despite a small sample size, these results are consistent with growing evidence that performance-based functional assessments may be a useful tool in identifying early changes related to ADRD. Key Points Question: Are performance-based functional assessments (PBFAs) sensitive to early white matter changes related to neurodegeneration? Findings: A PBFA related to medication management abilities was more sensitive to early white matter changes than traditional cognitive tests or self-/informant-report measures of daily function. Importance: Demanding functional assessments might be more sensitive than classic assessments to early neuropathological changes. Next Steps: Additional cross-sectional and longitudinal data in a diverse sample are needed to extend these results.