This study aimed to investigate perceptual body image and the relationship between perceived body image (PBI) and weight control differentiated according to obesity categories across the adult lifespan by sex among Koreans. We analyzed data on 10 198 adults aged 25 or older from the Korean National Health and Nutrition Examination Survey of a nationally representative sample of non-institutionalized Koreans. Significant discordance between PBI and body mass index (BMI) or waist circumference (WC) was found in all age groups in both sexes, and the discordance for obesity grew more severe with age. Linear associations between PBI and BMI or WC were found in normal weight and obese groups in all age groups in both sexes, with relatively greater BMI or WC differences for PBI found in obese men aged ≤64 or ≤44, respectively, and obese women of all ages or aged ≥75, respectively, compared to normal weight. Obese women aged ≥65 (BMI) or ≥75 (WC) and obese men in the 45-54 and 65-74 age groups (BMI and WC) had significant association between PBI and weight control. Interventions regarding accurate body size perception should be prioritized for obese women aged ≥65 or ≥75 and for obese men aged 45-54 and 65-74.