To　investigate　the　impact　of　physical　exercise　on　social-emotional　competence　in　primary　school　children,　and　to　examine　the　mediating　role　of　peer　attachment　and　the　moderating　role　of　gender.　A　stratified　sampling　method　was　employed　to　select　students　from　grades　3　to　6　in　six　primary　schools　located　in　the　eastern,　central,　and　western　regions　of　Hunan　Province.　The　PARS-3,　S-ECI,　and　Simplified　IPPA　were　administered,　resulting　in　the　collection　of　1180　valid　questionnaires.　(1)　Correlation　analyses　revealed　significant　positive　relationships　between　physical　exercise　and　social-emotional　competence,　physical　exercise　and　peer　attachment,　and　peer　attachment　and　social-emotional　competence.　(2)　Peer　attachment　partially　mediated　the　relationship　between　physical　exercise　and　social-emotional　competence　in　primary　school　children.　(3)　Gender　differences　were　observed　in　the　strength　and　direction　of　these　relationships,　with　boys　demonstrating　stronger　exercise-related　benefits　while　girls　exhibited　greater　developmental　gains　through　enhanced　peer　relationships.　Physical　exercise　is　associated　with　the　social-emotional　competence　of　primary　school　children　in　a　direct　positive　manner　and　can　also　be　linked　to　this　competence　through　the　mediating　of　role　peer　attachment.　Moreover,　gender　moderates　the　relationship　between　physical　exercise　and　social-emotional　competence,　with　physical　exercise　being　more　strongly　associated　with　boys’　social-emotional　competence　than　with　girls’.　However,　as　peer　attachment　increases,　girls’　social-emotional　competence　tends　to　develop　more　favorably　than　boys’.　These　findings　provide　a　theoretical　basis　for　developing　targeted　physical　exercise　interventions　to　promote　the　social-emotional　competence　of　primary　school　children.　©　The　Author(s)　2025.