The invention relates to a process for production of expanded thermoplastic elastomer, said process comprising the steps of: • (a) adding monomers and/or oligomers used for producing the thermoplastic elastomer with or without further starting materials into a first stage of a polymer-processing machine, • (b) mixing the monomers and/or oligomers and also the optionally added further starting materials and reacting the monomers and/or oligomers to give a polymer melt in the first stage of the polymer-processing machine, •(c) passing the polymer melt into a second stage of a polymer-processing machine and adding a physical blowing agent with or without further starting materials to obtain a polymer melt comprising a blowing agent, • (d) molding the polymer melt comprising a blowing agent into an expanded thermoplastic elastomer.