The objective of this study was to investigate changes in physical activity patterns associated with the COVID-19 pandemic in individuals with overweight and obesity who were participating in a school district worksite weight loss program. We conducted comparative design interrupted time series analyses on physical activity device (Fitbit) data from the 2018–2019 and 2019–2020 school years (N = 211). We administered a questionnaire in 2020 to supplement device data. After the stay-at-home orders in 2020, participants tended to decrease their weekly step count (B = −1315.7, SE = 627.7, p = .045), decrease their weekly “Lightly active minutes” (B = −39.1, SE = 12.6, p = .007), and increase their weekly “Very active minutes” compared to their counterparts from the year before (B = 7.6, SE = 3.2, p = .020). Decreased motivation, gym closures, and safety concerns were cited as barriers to physical activity. Having more time and health consciousness were cited as facilitators of physical activity. The COVID-19 pandemic was related to changes in physical activity in both positive and negative ways, revealing opportunities to promote healthy lifestyle behaviors in this population. More research is needed to determine optimal approaches to health promotion in the post-COVID-19 era.