The two-layered preform includes a tubular body having a mouth providing a neck at a first end thereof and a closed bottom at an opposite second end. At least part of the tubular body is formed by a first layer (P1) made of a primary molding material and a second layer (P2) made of an overmolding material. The first layer (P1) is an inner layer made of a primary molding material providing a barrier effect against light by absorption, and the second layer (P2) is an outer layer made of an overmolding material providing a barrier effect against light by reflection. The neck is formed with the overmolding material of the second layer (P2) not coated by the primary molding material of the first layer (P2).