A communication device for handling an open direct discovery comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The processing means is configured to execute the instructions stored in the storage unit. The instructions comprise receiving a discovery update message from a first proximity service (ProSe) function, wherein the discovery update message indicates a ProSe Application Code corresponding to a discovery filter or a ProSe Application ID corresponding to the ProSe Application Code; and stopping performing an open direct discovery according to the discovery filter.