Niigata City in Japan and Khabarovsk City in Russia signed a sister city agreement in 1965 and have been interacting with each other for a long time. We have been conducting comparative research on the elderly between the two cities, but there is no research on the young. Distorted perception of body weight and unnecessary dieting behavior in adolescent girls is considered a problem in both Japan and Russia. Therefore, the purpose of this study was to clarify the distortion of weight perception and diet behavior of adolescent girls in both the countries. In addition, it was decided to investigate the eating habits of people in both the countries. In total, 195 15-year-old girls from Niigata, Japan (October 2020) and 286 girls from Khabarovsk, Russia (February 2017) were surveyed. The questionnaire used was an excerpt from the World Health Organization survey on the health behavior of school-age children. The proportion of Japanese adolescent girls who perceived themselves as overweight (distorted body weight perception) was 60.5%, which was significantly higher than that of Russian adolescent girls at 30.1% (p < 0.001). In addition, the prevalence of weight loss behavior in Japan was 34.9% (n = 68), which was significantly higher than that in Russia with 27.3% (n = 78) (p < 0.001). Adolescent girls in Japan had more serious problems with weight perception, but had fewer problems with breakfast and vegetable intake habits than those in Russia. From a young age, perception of correct body shape and establishment of eating habits are important not only for current health but also for future health. We need to carefully educate adolescent girls that their body undergoes major changes through secondary sexual characteristics during adulthood.