Author's summary Circular RNAs were known to play vital role in myocardial ischemia reperfusion injury (MIRI), while the role of CircZNF609 in MIRI remains unclear. This study was aimed to investigate the function of CircZNF609 in MIRI. CircZNF609 aggravated the progression of MIRI via targeting miR-214-3p/PTGS2 axis, which suggested CircZNF609 might act as a vital modulator in MIRI.