Purpose <p>This study aims to systematically review the effects of High-Intensity Interval Training (HIIT) on physical fitness and physiological responses in taekwondo athletes.</p> Methods <p>Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic search was conducted across Web of Science, PubMed, Scopus, EBSCOhost, Embase, and CNKI on Dec 1^st, 2025. Methodological quality was assessed using the Physiotherapy Evidence Database scale, while risk of bias was evaluated using the Cochrane Risk of Bias tools. The certainty of evidence was further appraised using the GRADE framework. A DerSimonian–Laird random-effects model and inverse-variance method were employed for the meta-analysis. Subgroup analysis, sensitivity testing, and meta-regression were performed using R software.</p> Results <p>A total of 19 studies involving 503 taekwondo athletes were included in the systematic review, of which 14 were quantitatively synthesized in the meta-analysis. Meta-analysis indicated that HIIT resulted in significant improvements in cardiorespiratory endurance, anaerobic power and agility (<i>p</i> &lt; 0.05), whereas no statistically significant effects were observed for physiological response outcomes. Meta-regression analyses did not identify any training variables that were significantly associated with improvements in maximal oxygen uptake. The certainty of evidence for most outcomes was rated as low or very low, indicating that the strength of these conclusions should be interpreted cautiously.</p> Conclusions <p>HIIT improves cardiorespiratory endurance, anaerobic power and agility, while physiological response outcomes show no significant changes in taekwondo athletes. Due to the low certainty of evidence and the absence of identified moderators, further high-quality studies are warranted.</p> <p><i>Trial registration</i> PROSPERO registration number: CRD420251105792.</p> Graphical Abstract <p></p>