Post-COVID-19 condition (PCC) may impact mobility and balance and affect physical function. The objectives of the study were to estimate the prevalence of decline in balance and mobility in individuals with PCC; explore the association between comorbidities and sociodemographic characteristics with decline in balance and mobility; and evaluate correlations between decline in mobility and balance with change in performance of usual activities, personal care, and global health perception. The design was a cross-sectional study of persons with a COVID-19 diagnosis that was confirmed at least 3 months before the study. Those with PCC, defined as those still troubled by symptoms, were evaluated for decline in mobility and balance and with associated clinical and demographic factors using bivariate analysis and multivariable logistic regression. Correlations between decline in mobility and balance were also examined with change in ability to perform usual activities, personal care, and global health perception. In 1031 persons with PCC, mobility deteriorated in 44.9%, and balance deteriorated in 37.1%. Older age, hospitalization, comorbidities, and obesity were associated with decline in mobility, while decline in balance was associated with older age and comorbidities. Reduced mobility was associated with changes in ability to carry out usual activities (rp = 0.6), conduct personal care (rp = 0.6), and global health status (rp = 0.5). Correlations between decline in balance and these same outcomes were 0.5, 0.5, and 0.45, respectively. Almost half the participants with PCC had reduced mobility, and over a third reported deterioration in balance, with associated difficulties with daily functioning. Factors associated with greater decline help identify those most at risk. Many people with PCC experience changes in mobility and balance, which can affect functional capacities and lead to physical therapist consultations. Further study should assess specific needs of these patients and determine effective physical therapist interventions to meet these needs. Many persons with post-COVID-19 condition (PCC) experience symptoms resulting in functional problems, such as difficulties with personal care and performing usual activities. This study focused on difficulty in mobility and problems with balance. Almost half of persons with PCC in the study had declines in getting around and over a third had declines in balance. These problems were associated with older age and having other comorbid health conditions and were linked with decline in ability to perform personal care, carry out usual activities, and perceived global health status.