This article proposes an extensive experimental and microstructural analysis to study the consequences of deep cryogenic treatment (DCT) soaking duration on tungsten carbide end mill cutter on the machinability of P20 mold steel. A Box-Behnken design of response surface methodology (RSM) is utilized to collect data for the study. Cutting speed, feed rate, depth of cut and milling cutters subjected to various soaking durations are taken as important process variables which are a function of performance measures viz. tool wear rate (TWR), material removal rate (MRR) and surface roughness (R a). It is observed that cutting speed, feed, depth of cut and cryogenic treatment exhibit a considerable effect on performance measures. In the present study, NSGA-II multi-objective optimization technique is used to obtain the optimal process parameters of end milling process to enhance the productivity of the process. For this purpose, the developed RSM model is coupled with NSGA-II in MATLAB. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.