An integrated circuit device package may include a flexible substrate having a first wiring, an integrated circuit device having a second wiring, a flexible insulation structure having a first opening and a second opening exposing the first wiring and the second wiring, respectively, a third wiring electrically connecting the first wiring to the second wiring, and a flexible protection member covering the third wiring. A stacked flexible integrated circuit device package may include a flexible substrate, a first flexible integrated circuit device including a first connection pad, a second flexible integrated circuit device including a second connection pad, a connection wiring electrically connecting the first and the second connection pads to an external device, and a flexible protection member disposed on the second flexible integrated circuit device.