Abstract Introduction Evidence on long-term associations between coronavirus disease 2019 (COVID-19) and risks of multi-organ complications and mortality in older population is limited. This study evaluates these associations. Research design and methods The cohorts included patients aged ≥60 year diagnosed with COVID-19 infection (cases), between 16 March 2020 and 31 May 2021 from the UK Biobank; and between 01 April 2020 and 31 May 2022 from the electronic health records in Hong Kong. Each patient was randomly matched with individuals without COVID-19 infection based on year of birth and sex and were followed for up to 18 months until 31 August 2021 for UKB, and up to 28 months until 15 August 2022 for HK cohort. Patients with COVID-19 infection over 6 months after the date of last dose of vaccination and their corresponding controls were excluded from our study. Characteristics between cohorts were further adjusted with Inverse Probability Treatment Weighting. For evaluating long-term association of COVID-19 with multi-organ disease complications and mortality after 21-days of diagnosis, Cox regression was employed. Result 10,759 (UKB) and 165,259 (HK) older adults with COVID-19 infection with matched 291,077 (UKB) and 1,100,394 (HK) non-COVID-19-diagnosed older adults were recruited. Older adults with COVID-19 were associated with a significantly higher risk of cardiovascular outcomes [major cardiovascular disease (stroke, heart failure and coronary heart disease): hazard ratio(UKB): 1.4 (95% Confidence interval: 1.1,1.6), HK:1.2 (95% CI: 1.1,1.3)]; myocardial infarction: HR(UKB): 1.8 (95% CI: 1.3,2.4), HK:1.2 (95% CI: 1.0,1.4)]; respiratory outcomes [interstitial lung disease: HR(UKB: 3.4 (95% CI: 2.5,4.5), HK: 4.0 (95% CI: 1.3,12.8); chronic pulmonary disease: HR(UKB): 1.7 (95% CI: 1.3,2.2), HK:1.6 (95% CI: 1.3,2.1)]; neuropsychiatric outcomes [seizure: HR(UKB): 2.6 (95% CI: 1.7,4.1), HK: 1.6 (95% CI: 1.2,2.1)]; and renal outcomes [acute kidney disease: HR(UKB): 1.4 (95% CI: 1.1,1.6), HK:1.6 (95% CI: 1.3,2.1)]; and all-cause mortality [HR(UKB): 4.9 (95% CI: 4.4,5.4), HK:2.5 (95% CI: 2.5,2.6)]. Conclusion COVID-19 is associated with long-term risks of multi-organ complications in older adults (aged ≥ 60). Infected patients in this age-group may benefit from appropriate monitoring of signs/symptoms for developing these complications.