Obesity is a worldwide epidemic problem. The downward trend of an obesity onset age calls for research efforts on how to develop useful nutrition educational programs for children to maintain adequate body weight. Understanding the roles of objective and subjective body status in obesity-related attitudes, knowledge, and behaviors can provide important information. The current study aimed to examine obesity-related attitudes and knowledge and practices of eating behavior guidelines in relation to obesity and body shape satisfaction among children. The gender effect in the relations was also investigated. A self-administered survey was conducted with 260 fifth grade children at 2 public elementary schools in the suburbs of Seoul. Information on demographics, body size, body satisfaction, obesity-related attitudes and knowledge, and eating behaviors was collected. Study findings from one-way analysis of variance tests indicated no differences in mean scores of the attitudes, knowledge, and eating behaviors across the levels of obesity for both gender. The levels of body shape satisfaction was, however, found to be significantly related with the attitudes and eating behaviors in girls, while no such relation was seen in boys. Girls with lower body shape dissatisfaction had significantly more negative attitudes toward obesity which was not translated into practice of healthy eating behaviors. That is, contrary to general expectation, the level of practicing the eating behavior guidelines was significantly lower in those girls. While underlying reasons for this observation is not fully answered, gender-specific, body satisfaction-stratified, and behavior-focused approach in designing obesity prevention programs for elementary school girls is suggested efficient and useful.