Obesity is an established risk factor for severe influenza and is classified as a high-risk condition by national and global health authorities. However, previous studies show inconsistent evidence on whether obese individuals are more likely to receive influenza vaccination in Korea. With substantial shifts in vaccination policies and population behavior surrounding the COVID-19 pandemic, updated evidence is needed.To investigate whether obesity shows independent association with influenza vaccination among Korean adults, and to assess whether this association varies by survey year or sex.We analyzed national representative data from KNHANES 2019–2023. Adults aged ≥20 years with available BMI and vaccination data were included. Obesity was categorized according to Korean BMI criteria: normal (<25.0 kg/m²), stage I (25.0–29.9 kg/m²), and stage II+ obesity (≥30.0 kg/m²). Vaccination status was self-reported as yes or no. Survey-weighted logistic regression assessed associations adjusting for age, sex, education, income, and region. Additional analyses included sex-stratification and year-specific models.A total of 16,242 adults from 2019-2021, and 10,560 from 2022-2023 were analyzed. Higher BMI groups showed slightly higher vaccination rates (e.g., 2019: normal 41.1% vs. stage I+ 44.0%, 2022: normal 40.0% vs. stage I+ 44.8%), but differences were not statistically significant. In adjusted models, none of the obesity stages showed significant association across the entire period. Most year-specific analyses also displayed no significant association before or after COVID-19. However, in 2022, individuals with stage I+ obesity showed significantly higher odds of vaccination (OR 1.14, 95% CI 1.02–1.27), but this association did not persist when divided into more detailed BMI stages.Obesity did not independently predict influenza vaccination. Demographic and socioeconomic factors such as age, sex, and income were stronger determinants. The temporary increase in 2022 may reflect heightened risk perception and public-health messaging during the early post-pandemic period.Obesity does not appear to be a major determinant of vaccination among Korean adults. Improving vaccination coverage may require addressing socioeconomic and demographic barriers rather than focusing solely on weight status. Further research is required to identify subgroups within the obese population who may benefit from targeted vaccination strategies.