An apparatus for preventing a malfunction of a peripheral device in a portable terminal with multiple processors includes a battery, a peripheral device electrically connected to a switch through a I/O pins, a first processor in which a control port for the peripheral device is electrically connected to the switch through the GPIO method, and which controls driving of the peripheral device through generation of a normal high signal, a second processor electrically connected to the switch through the GPIO method, and the switch driven by the battery, configured to operate such that the control port of the first processor is grounded when it is determined that an unintended high signal is generated from the second processor before the portable terminal is completely booted.