An actuating mechanism for a window shade includes an electric motor for driving a displacement of a movable rail, a motor controller electrically coupled to the electric motor and having a first and a second connector, a power supply, a wired control interface, and a removable wireless adapter operable to convert a wireless signal outputted by a wireless control interface to an electric signal. The actuating mechanism has a first configuration supporting wireless control, and a second configuration supporting wired-only control, the wireless adapter being respectively connected with the power supply, the wired control interface and the first and second connectors of the motor controller in the first configuration, and the wireless adapter being removed and the power supply and the wired control interface being respectively connected with the first and second connectors of the motor controller in the second configuration.