A camera accessory is detachably engaged with a camera body including a camera body mount and body-side electric contact points. The camera accessory includes a camera accessory mount assuming a bayonet structure with a first tab, a second tab and a third tab. The camera accessory mount is configured to be inserted through the camera body mount without any of the first through third tabs hindered by three camera body-side tabs disposed at the camera body mount as long as the camera accessory mount is inserted at the camera body mount at a correct interlock phase. The camera accessory mount is configured such that insertion of the camera accessory mount through the camera body mount is disallowed at any phase other than the correct interlock phase with at least two tabs among the first through third tabs coming into contact with at least two of the camera body-side tabs.