The object of the invention is a method for extracting, with high yield, phycobiliproteins from cyanobacterial and/or algal biomass, obtaining extracts in water or aqueous solutions characterised by high pigment concentration and a purity degree equal to or greater than the food/cosmetic grade (P≥2). The method is based on a process characterised by a step of breaking down the cyanobacterial/algal cells by ultrasonication in an aqueous solution of ammonium sulphate, and simultaneous extraction of water-soluble compounds other than phycobiliproteins, followed by an extraction step of the phycobiliproteins using water or aqueous solutions.