Abstract The performance of Stirling cryocooler is governed by principal designparameters. The optimum combination of these design parameters gives maximum refrigeration effect and minimum desired efforts. The performance of the cryocooler depends significantly on the regenerator functioning and the working fluids. The mesh size of the regenerator affects dead space, pressure drop, regenerator effectiveness, etc. The working fluids differ in their thermal properties and therefore affect the performance significantly, The present paper aims to study the influence of regenerator matrix and working fluids on these design parameters. The matrix material considered is Phosphor Bronze while the working fluids considered are Helium and Hydrogen.