Seniors’ mobility decreases as they age as a result of deteriorating health and restricted travel alternatives. Consequently, it is imperative that their transportation needs be met, particularly when they are at risk because of pandemics like COVID-19. This study aims to examine older U.S. citizens’ (65 years and older) travel behavior and challenges before and during COVID-19 through conducting a nationwide online survey that collected responses from 1,507 senior U.S. citizens. The McNemar-Bowker test and Ordered Probit Modeling were employed to assess the differences in their travel behavior and factors determining their mobility satisfaction during COVID-19. The findings indicate that there was a considerable reduction in the frequency of work-related, shopping, medical, leisure, and social/religious trips during COVID-19. In addition, the frequency of all travel modes usages declined significantly except for paratransit and motorcycle. Senior U.S. citizens’ travel choices during COVID-19 were largely influenced by their safety and security, virus infection concern, and comfort and convenience. Seniors mostly preferred to use their private vehicles during COVID-19. Accessibility, reliability, and flexibility were the greatest concerns of seniors about using public transit. Moreover, seniors’ satisfaction with their mobility depended on their physical mobility challenges, family size, subregional locations, length of driving, decline in their driving skills and abilities as they aged, preference to use private cars as the most affordable and reliable modes, and extra expenditure they made on their travels during COVID-19. Finally, several actionable countermeasures have been suggested in this study to improve the mobility of seniors.