BACKGROUND: Declining cognition is a risk factor for falls among older adults. The extent to which impaired judgment in performance of daily activities increases fall risk is unclear. OBJECTIVE: The aim of this study was to determine whether engagement in mobility activities in a risky manner explains the association between declining cognition and rate of falls. DESIGN: This study was a secondary analysis of baseline and prospective data from older adults enrolled in the intervention arm of a randomized clinical trial. METHODS: Two hundred forty-five community-dwelling older adults (79% female; mean age=79 years, SD=8.0) who were at risk for falls received physical, cognitive, and functional evaluations. Cognition was assessed with the Short Portable Mental Status Questionnaire (SPMSQ). Using interview and in-home assessment data, physical therapists determined whether participants were at risk for falls when performing mobility-related activities of daily living (ADL) and instrumental ADL (IADL). Falls were measured prospectively for 1 year using monthly falls diaries. RESULTS: Declining cognition was associated with increased number of mobility activities designated as risky (1.5% of mobility activities performed in a risky manner per SPMSQ point) and with increased rate of falls (rate ratio=1.16 for each unit change in SPMSQ score). Risky performance of mobility activities mediated the relationship between cognition and rate of falls. LIMITATIONS: Risk assessment was based on the clinical judgment of experienced physical therapists. Cognition was measured with a relatively insensitive instrument, and only selected mobility activities were evaluated. CONCLUSIONS: Engagement in mobility ADL and IADL tasks in a risky manner emerged as a link between declining cognition and increased number of falls, suggesting a mechanism through which the rate of falls may increase. Specifically, declining cognition is associated with performance of mobility activities in an unsafe manner, thereby increasing the risk for falls.