A ventilation assembly of the present disclosure includes: an internal member being a tubular body having an opening at a first end portion and an opening at a second end portion; an external member being a tubular body having a bottom; and a gas-permeable membrane covering the opening at the first end portion of the internal member, wherein the external member is joined to the internal member with the internal member inserted in the interior of the external member from the first end portion side, the ventilation assembly has a second space serving as a ventilation path connecting the gas-permeable membrane and the outside of the ventilation assembly in at least one selected from the inside of the internal member, the inside of the external member, and an interspace between the internal member and the external member joined together, and the internal member includes one first projecting portion or two or more first projecting portions projecting from the inner peripheral surface at a position on the second end portion side with respect to the gas-permeable membrane. The ventilation assembly of the present disclosure can prevent the gas-permeable membrane from being damaged at the time of fixation to the projection even when the ventilation assembly is reduced in height.