The present study's objective was to determine the relation between hamstring flexibility and body composition in children who were active indoors during the pandemic. The study included 25 children, ages 8 to 14, who were physically active indoors over the previous month but did not participate in outdoor activities. The body composition of the participants was evaluated using the BMI and body fat percentage, and the sit-and-reach test was used to assess hamstring flexibility. Karl Pearson's Correlation Coefficient was used to find a relationship between hamstring flexibility and body composition. According to the results, BMI and hamstring flexibility has a statistically significant weak negative correlation (r = -0.44, p = 0.02), although body fat % and hamstring flexibility has a non-statistically significant weak negative correlation (r = -0.35, p = 0.08). Thus, it can be concluded that BMI is negatively correlated with hamstring flexibility in children who were active indoors during the pandemic. However, a study correlating body fat percentage with hamstring flexibility in a larger population is required for further clarification.