Rheumatic heart disease (RHO) is a sequela of acute rheumatic fever (ARF) caused by the delayed immune response after group A β-hemolytic Streptococcus (GABHS) infection. It is the most frequent etiology of permanent heart valve damage in pediatrics, especially in the mitral valve. Interleukin-17 (IL-17) is cytokines that associate with the pathogenesis of RHO. Repeated exposure to GAHBS with an excessive Th17 response is thought to trigger inflammation, which will increase the severity of valve damage in RHO. This study aims to determine how circulating IL-17 level plays a part in the progression of mitral regurgitation (MR) in pediatric patient with RHO. The cross-sectional study included children 5-18 years diagnosed with ARF and RHO divided into 4 groups: mild, moderate, severe MR, and ARF without heart valve damage. ELISA method was employed to observe IL-17 levels, and comparison was made in each group. The levels of circulating IL-17 had a significant difference compared to each group of MRs (p = 0.000). Increasing IL-17 level associated with worse degree of MR with a strong positive correlation (p = 0.000, r = 0.638). There was a positive correlation of circulating IL-17 level and progression MR in the pediatric patient with RHD.