This study investigated the risk of post-COVID-19 conditions in older patients with COVID-19 compared to those with influenza, and how age impacts this relationship. Patients aged ≥65 years with COVID-19 or influenza were identified using the TriNetX network. The risk of post-COVID-19 conditions was compared between survivors of COVID-19 and influenza, followed by a comparison of post-COVID-19 conditions risk between patients aged 65–74 years and those aged over 75 years. Compared with influenza survivors, post-COVID-19 conditions were significantly more prevalent in patients with COVID-19 (hazard ratio [HR], 1.534; 95% confidence interval [CI]: 1.405–1.675). Specifically, COVID-19 survivors have a significantly higher risk of experiencing abnormal breathing (HR, 2.052; 95% CI: 1.757–2.397), fatigue (HR, 1.587; 95% CI: 1.322–1.905), anxiety/depression (HR, 1.587; 95% CI: 1.322–1.905), cognitive symptoms (HR, 1.667; 95% CI: 1.295–2.146) and cough (HR, 1.250; 95% CI: 1.006–1.553) compared with the influenza group. Contrastingly, no significant difference was observed in the risk of any post-COVID-19 condition between COVID-19 survivors aged 65–74 years and those aged over 75 years (HR, 0.994; 95% CI: 0.920–1.073). However, a lower incidence of cognitive symptoms was observed in patients aged 65–74 years compared to those aged ≥75 years (HR, 0.543; 95% CI: 0.445–0.661). In conclusion, compared with influenza, older patients have a higher risk of developing post-COVID-19 conditions after SARS-CoV-2 infection, and those aged over ≥75 years may have an increased risk of developing cognitive symptoms compared to those aged 65–74 years.