An apparatus and method for controlling transmit power of an electronic device in a wireless communication system are provided. A proposed method for a base station as a master node of an electronic device in an evolved universal terrestrial radio access (E-UTRA) new radio (NR) dual connectivity (EN-DC) environment to communicate with the electronic device via a first radio access technology (RAT) in a first band includes performing a random access procedure with the electronic device, inquiring and receiving electronic device capability information from the electronic device, determining whether to add a secondary node supporting communication with the electronic device via a second RAT in a second band that is different from the first band, and transmitting an updated power allocation value to the electronic device along with a secondary node addition command based on the electronic device capability information indicating that the electronic device does not support dynamic power sharing, the update power allocation value being set based on the electronic device capability information and uplink power information for transmission to the second node.