Selection of the optimum electrochemical machining (ECM) process parameters is extremely crucial as this machining process involves huge capital investment and operating cost. In this work, the harmony search (HS) algorithm is integrated with desirability function (DF) in such a way that new HS-DF optimiser is proposed to optimise the ECM process parameters. The influence of three predominant ECM process parameters i.e. inter-electrode gap (IEG), voltage (V) and electrolyte concentration (EC) on the performance measures of material removal rate (MRR) and surface roughness (Ra) was considered. The optimised values of EC = 115 g/l, V = 13 V, and IEG = 0.11 mm resulted in MRR of 0.726 g/min and Ra of 1.53 μm for electrochemical machining of Monel 400 alloys. The optimised results are compared with those drawn from the past research and found better. The HS-DF optimiser proves its applicability and suitability for optimising process parameters of ECM process, which reduces considerable computational, experimental cost and time. Copyright © 2020 Inderscience Enterprises Ltd.