Objective: Non-mercury sphygmomanometers are essential for international mercury reduction initiatives and sustainable surveys. This research compares an automated oscillometric device (OD) with a hybrid manual auscultatory device (AD) to determine an appropriate BP measurement device for children in the Korea National Health and Nutritional Examination Survey (KNHANES). Design and method: In 2022, a survey of 251 children, evenly distributed by gender and age (6-12 and 13-18 years), was conducted following KNHANES protocols and BP measurement guidelines, with informed consent obtained from children and parents. The Microlife WatchBP Office AFIB® (OD) and Greenlight 300TM® (AD) were evaluated based on the 2018 Universal Standard guidelines (USG). To avoid memory bias, AD measurements were taken before OD. BP differences were calculated by subtracting AD values from OD values. Analysis of mean device differences by gender, age, and measurer was performed using Pearson’s correlation, Lin’s concordance correlation coefficients (CCC), and Bland-Altman plots with limits of agreement (LOA). Results: The BP differences (SBP/DBP) were 1.2 ± 6.3 / -0.7 ± 6.3 mmHg for boys and –0.8 ± 5.2 / -2.2 ± 5.8 mmHg for girls. The proportions of BP differences within ±10 mmHg were 90.1% (SBP) and 89.3% (DBP) for boys, and 93.8% (SBP) and 86.9% (DBP) for girls. Overall CCC for SBP and DBP were 0.79 and 0.60. For boys, CCCs were 0.76 (SBP) and 0.63 (DBP), while for girls, they were 0.77 (SBP) and 0.56 (DBP). In the 6-9 age group, CCCs were 0.80 (SBP) and 0.53 (DBP); in the 16-18 age group, they were 0.82 (SBP) and 0.68 (DBP). The LOA ranged from -11.34 to 11.66 mmHg for SBP and -13.31 to 10.42 mmHg for DBP, indicating broader variability in boys. Conclusions: The results obtained from OD aligned with those of the USG; however, the concordance rate was observed to be reduced in DBP relative to SBP, particularly in younger age groups. Given the importance of childhood BP for future health, further research should aim to establish a comprehensive database of BP measurements in children across all genders and ages.