Provided is a method of fabricating a battery protection circuit package, the method including preparing a complex package substrate obtained by connecting a flexible printed circuit board (PCB) including at least one external connection terminal for connection to an external device, to a rigid PCB for mounting components thereon, mounting the complex package substrate on a lead frame including at least one metal tab for connection to a battery cell, and encapsulating at least portions of the complex package substrate and the lead frame with a molded part while exposing the at least one metal tab and the at least one external connection terminal.