Abstract: A protecting case assembly with foldable slim speaker for portable apparatus includes a protecting case attached with two hinge members and two slim speakers, like electret speakers, each attached with a hinge. Two hinges are correspondingly connected to the two hinge members so as to make the two slim speakers be rotatable between a close position and an open position. Furthermore, a resonance chamber of the protecting case receives a woofer. Next, the protecting case assembly can receive external multimedia signals from a portable apparatus through a Bluetooth module and output the signals through the electret speakers and the woofer to perform high quality sound effects. Therefore, according to the protecting case assembly, the user can use it to protect the portable apparatus whilst conveniently carrying better sound equipment in order to enjoy a high quality audio and video performance anytime and anywhere.