Abstract. Maximizing independent function during the progressive decline of balance and mobility in older adults with chronic diseases, such as Parkinson's disease (PD), is a unique challenge for rehabilitation. Balance training to reduce fall risk is a critical feature of rehabilitation for older adults, especially those with PD. However, the recent COVID-19 pandemic has uncovered serious weaknesses in safely and effectively delivering balance rehabilitation in people's homes. In fact, balance rehabilitation, for the most part, has been deferred during the pandemic due to inability of tele-rehabilitation to remotely assess balance skills, exercise task performance, or transfer of balance skills into daily life. We hypothesize that using objective measures for balance assessment remotely will improve outcomes and that telerehabilitation is feasible using state-of-the- art, evidence-based balance rehabilitation. In 80 people with PD, we will use state-of-the-art wearable sensors to objectively measure balance in the home and in daily life passive monitoring. In Aim I, we will determine if a virtual, instrumented balance assessment using wearable sensors can predict performance on our gold standard, clinical in-person balance assessment (Mini-BESTest). In Aim II, we will determine the feasibility and efficacy of a balance-focused tele-rehabilitation. For this Aim people will be randomized into either unsupervised home exercises (standard of care) or 2) physical therapist-supervised, balance tele-rehabilitation. In Aim III, we will explore if improvements after tele- rehabilitation transfer to daily life mobility, measured with 7 days of passive monitoring. This project will determine the feasibility and efficacy of using wearable sensor-based measures of balance and gait to improve virtual assessment of balance in people with PD. Moreover, we will explore how tele-rehabilitation improves balance and if the improvement translates to daily mobility. This outcome of this project will help develop a more effective home-based balance and rehabilitation assessment and treatment that can be used in any older adults with balance impairments.