A method and apparatus for preventing unauthorized use of a mobile terminal are provided, in which an execution code processor decrypts an Mobile Phone Certificate (MPC) using an MPC decryption code stored in it, when the mobile terminal is booted, an MPC processor compares a pre-stored MPC decryption execution code with the MPC decryption execution code, compares a pre-stored MPC encryption key with an MPC encryption key stored in the execution code processor. When the MPC decryption execution codes are identical, sets data required for an initial operation of the mobile terminal using an MPC management execution code included in a pre-stored MPC. When the MPC encryption keys are identical, decrypts Secured Code (SCode) blocks for execution of an application program, after executing the MPC management execution code. The execution code processor performs an operation program of the mobile terminal using the MPC management execution code and the decrypted SCode blocks.