Since the Russian invasion of Ukraine on Feb 24, 2022, more than 6 million Ukrainians, including hundreds of thousands of older people, have sought safety abroad. Older people generally have a higher burden of disease than younger people and the aim of our study was to estimate this burden in older Ukrainian refugees, given the potential financial and logistical impacts on the health-care systems of receiving countries. On May 20, 2022, we searched the official websites of the Polish Ministry of Digitisation for data on Ukrainian refugees who had applied between Feb 24, 2022, and May 19, 2022 for a Polish personal identification number (PESEL). We extracted the number of older people (ie, of pension age, which in Ukraine is 60 years or older for men, and 55 years or older for women). We calculated the percentage of older people among these PESEL applicants then extrapolated this percentage to two groups, for which population data had been extracted from UN, WHO, and Polish Border Guards websites: refugees who had crossed into Poland but had not applied for a PESEL and refugees who had fled to neighbouring countries other than Poland. Between April 4 and May 19, 2022, we searched the Ukrainian Ministry of Health official website for data on the prevalence and incidence of various diseases in the Ukrainian population of older people. We asked the Ukrainian Ministry of Health to confirm and expand on the website data, and thereby obtained annual data for 2010-17. The ministry did not supply tuberculosis statistics, so on May 21, 2022, we searched the Ukrainian Ministry of Health website and extracted the most recent tuberculosis data, which were for 2020. We then calculated the absolute prevalence and incidence of diseases in older refugees. As of May 19, 2022, 6·3 million Ukrainians had fled their country, including 3·5 million (56%) who had entered Poland. 1 114 418 people applied for a PESEL, including 109 985 older people (91 349 Ukrainian women aged 55 years or older and 18 636 Ukrainian men aged 60 or older). We estimated that the overall number of older Ukrainian refugees was 624 690. We estimated that these older refugees have a mean of 2·5 diseases each, the most frequent of which are cardiovascular diseases, followed by gastrointestinal, respiratory, musculoskeletal, and genitourinary diseases. We estimated that the expected absolute incidence is greatest for pulmonary disorders (71 689 diagnoses), followed by cardiovascular (49 327), ocular (24 100), musculoskeletal (20 367), and genitourinary (16 836) disorders. The estimated number of new diagnoses per year was 4578 for tuberculosis and 7827 for cancer. Our data indicate that the disease burden of older Ukrainian refugees is considerable. Although our estimates are only approximations, they provide a basis for predicting which areas of health care will most need to be reinforced to meet the challenge of the potential financial and logistical impacts on receiving countries. There was no funding source for this study.