The accessory is detachably attachable to an image capturing apparatus. The accessory includes a communicator configured to communicate with the image capturing apparatus in multiple communication modes, and a communication mode setter configured to set one of the multiple communication modes which corresponds to command information received from the image capturing apparatus as a use communication mode used to communicate with the image capturing apparatus. The communication mode setter is configured to set the use communication mode corresponding to the command information in response to reception of the command information and reception of first correspondence information different from the command information and in correspondence with the command information, from the image capturing apparatus.