An accessory includes a case body, a cover unit, and first and second coupling units. The case body is formed with a receiving space for receiving a portable electronic device. The cover unit is configured to be coupled removably to the case body for closing and opening the receiving space. The first coupling unit includes a data and charge connector for mating electrical connection with a data and charge socket of the portable electronic device, and a data and charge port connected to the data and charge connector. The second coupling unit includes a connector jack for mating electrical connection with an audio socket of the portable electronic device, and an audio port connected to the connector jack.