Abstract Background We assessed whether clinical, functional and behavioral factors were associated with the decrease in mobility trajectories reported in older people at risk of sarcopenia (RS) and without risk of sarcopenia (NRS) during COVID-19 pandemic. Methods We prospectively analyzed mobility trajectories reported in older adults with RS and NRS over 16-month follow-up (Remobilize study). The self-perceived risk of sarcopenia and mobility were assessed using the SARC-F and the Life-Space Assessment (LSA) tools, respectively. Gender, age, comorbidities, pain, functional limitation, physical activity (time spent in walking; min/week), and sitting time (ST; hours/day) were assessed. We used a multilevel model to determine changes in mobility between groups and over time. Results Mobility was lower in RS than in NRS. Older people at RS, who were women, aged 70–79 years and 80 years or older, inactive, and with moderate to severe functional limitation experienced reduced mobility trajectories reported over the pandemic. For older people at NRS, trajectories with reduce mobility reported were experienced by women with comorbidities, for those with insufficient walking time and aged 70–79 years; aged 70–79 years and with ST between 5 and 7 hours/day; for those with insufficient walking time and increased ST; and for those with pain and increased ST. Conclusion Mobility trajectories reported in older people at risk of sarcopenia were negatively influenced by insufficient level of physical inactivity and pre-existing moderate to severe functional limitation. Health and social interventions should be target to avoid mobility limitation during and after the COVID-19 pandemic.