Abstract: The invention relates to a perimetral slab formwork system applicable for configuring a cantilever on a base grid formwork, configured by primary beams between which formwork panels are housed. In one possible solution, it incorporates perimetral beams provided with connectors for coupling on props and a straining piece which is vertically placed between outer and inner perimetral formwork panels supported by the perimetral beams to aid in lowering a formwork stripping tool connected to the outer panels. In another solution for smaller cantilevers, it has second perimetral beams having a matching configuration with the primary beams extending with regard to the base formwork combined with perimetral clamps fitting in one of their ends provided with a connector for a prop and housing for railings.