A vehicular occupant restraint system including: a four-point seatbelt system having left and right webbings for restraining an occupant, each of the left and right webbings having an upper body restraining portion that restrains the upper body of the occupant; a left first inflating portion which is provided on the upper body restraining portion of the left webbing and which inflates by receiving a gas supply and deploys in front of the upper body of the occupant, and a right first inflating portion which is provided on the upper body restraining portion of the right webbing and which inflates by receiving a gas supply and deploys in front of the upper body of the occupant; and a second inflating portion which inflates by receiving a gas supply when the first inflating portions inflate, and deploys to support the first inflating portions from the outside in the seat width direction.