Social anxiety disorder is a common psychological problem that may negatively impact the cognitive and social development of children. Its severity may, however, be reduced through regular participation in sports or other physical activity. This study aimed to determine the relationship between competitive student-athlete swimmers' social anxiety levels and anthropometric measurements (height, weight, and BMI), body composition (body fat and lean body mass), and body type (ectomorph, endomorph, or mesomorph). The participants were pre-adolescent female and male lower secondary education student-athlete swimmers. The Social Anxiety Scale was used to evaluate their social anxiety levels, while the anthropometric parameters included height and weight, from which BMI was calculated. Body composition involved determining the percentage of body fat and lean body mass; ectomorphic, endomorphic, and mesomorphic values were then calculated. We found that the social anxiety levels of both female and male student-athlete swimmers were low. There was no statistically significant relationship between the social anxiety levels of the male and female student-athlete swimmers with BMI, lean body mass, or ectomorphy. For the female swimmers, social anxiety levels were not associated with body fat, endomorphy, or mesomorphy, nor were those of the male student-athlete swimmers. These findings suggest that participation in competitive swimming during adolescence is effective in controlling social anxiety. Furthermore, this study revealed that social anxiety is not associated with lower secondary education student-athlete swimmers' anthropometric measurements, body composition, or body type.