The mould with an internal shaping core for manufacturing thin-walled blown glass objects, for example Christmas tree decorations, consists of at least two semi-moulds with a free mould division axes, matched and connected disjointly with an opening for inserting the stay for blowing the air inside the mould. The shaping core fastened inside the mould is stabilised in at least one seat or lock through full closure of both semi-moulds. In the thus shaped spatial cavity a heated glass bulb is blown up which is given a final, monolithic complex shape.