A method of and apparatus for synchronizing interactive contents. The apparatus includes a synchronized multimedia element determining unit and an application program interface (API). The synchronized multimedia element determining unit determines whether multimedia elements included in the interactive contents are synchronized with audio video (AV) contents. The API transmitting unit transmits an API corresponding to an interactive control command to an AV contents reproducing engine that reproduces the AV contents and a synchronized multimedia element reproducing engine that reproduces multimedia elements that are determined by the synchronized multimedia element determining unit to be synchronized with the AV contents.