The special characteristics of microplasma such as microscale geometry, atmospheric operation, self-organization property, and high radical density are suitable for the synthesis of nanoparticles. Trimanganese tetroxide (Mn 3 O 4) nanoparticles (NPs) were synthesized through plasma reduction mechanism by the use of sustainable, rapid, and microplasma array method at atmospheric conditions in a single step. 96.10% reaction yield of hausmannite Mn 3 O 4 NPs were gained by the reduction of potassium permanganate (KMnO 4) precursor solution in the presence of radicals in the microplasma discharge with a processing time of 30 minutes. The structure, oxidation state, morphology, composition, and specific surface area of synthesized particles were determined by XRD, FTIR, XPS, FE-SEM with EDX, HR-TEM, and BET characterization techniques. Spherical polydisperse particles with high surface area (304.01 m 2 g −1) and narrow distribution were obtained. The performance of synthesized Mn 3 O 4 NPs as an electrode material for supercapacitor application was analyzed by electrochemical workstation, which exhibited a high specific capacitance of 144.5 Fg −1 at a current density of 0.5 Ag −1 and the electrode material retained 43.54% of its initial capacitance after 1500 cycles. The asymmetric performance of Mn 3 O 4 NPs as one of the electrode materials exhibited high cyclic stability with 100% retention capacitance with an energy density of 3.33 Wh kg −1 at 0.1 Ag −1 and high power density of 422.5 W kg −1 at 0.5 Ag −1 , respectively. The present study gives new perspectives on a simple, efficient, eco-friendly, and powerful microplasma array method for the coalescence of Mn 3 O 4 NPs and the analysis of electrochemical behavior of corresponding NPs. K E Y W O R D S electrochemical performances, microplasma discharge, Mn 3 O 4 nanoparticles, supercapacitor 1 | INTRODUCTION The rapid growth of technology in all the aspects of our human and societal life has brought about many changes [Correction added on 10 February 2021, after first online publication: reference citations and Figure 13 have been corrected.]