A semi-synthetic platelet gel comprising a platelet-rich plasma, at least one platelet activator, and a biocompatible polymer selected from the group comprising carbomers, polyalkylene glycols, poloxamers, polyesters, polyethers, polyanhydrides, polyacrylates, polyvinyl acetates, polyvinyl pyrrolidones, polysaccharides, and derivatives thereof. A method for preparing a semi-synthetic platelet gel comprising the steps of (a) mixing a platelet-rich plasma with at least one platelet activator, and, before the start of clot formation, (b) adding the mixture thus obtained to a biocompatible polymer selected from the group comprising carbomers, polyalkylene glycols, poloxamers, polyesters, polyethers, polyanhydrides, polyacrylates, polyvinyl acetates, polyvinyl pyrrolidones, polysaccharides, and derivatives thereof.