Disclosed is a side curtain airbag and an airbag system including the same. The side curtain airbag according to the present invention comprises an inflating part having gas inflation, a non-inflating part supporting the inflating part, and an adhered part constituting a boundary between the inflating part and the non-inflating part. The adhered part is coated with a seam sealant and sewed. The initial maximum pressure of the inflating part is 40 kPa or more when injecting a gas therein with an instant pressure of at least 10 bar, and the pressure after 6 seconds is 25 kPa or more. The side curtain airbag may optimize to apply the method of seam sealant coating and sewing on the adhered part constituting a boundary between the inflating part and the non-inflating part. Thus, it can keep the internal gas pressure of the airbag to the extent of protecting passengers safely at rollover.