A method of handling simultaneous communications comprises a first base station configuring a radio resource control (RRC) connection to a communication device; the first base station configuring a second base station as a secondary base station to the communication device; the second base station configuring a signalling radio bearer (SRB) to the communication device via the first base station; the second base station transmitting a second measurement configuration to the communication device; the second base station receiving a second measurement report corresponding to the second measurement configuration via the SRB from the communication device; and the second base station adding a secondary cell (SCell) of the second base station to the communication device, releasing a SCell of the communication device, or changing a primary secondary cell (PSCell) of the communication device via the first base station or via the SRB.