The plate heat exchanger (PHE) is an important component for parameters such as size, weight, high temperature and high pressure in many nanotechnological applications. Improving the thermo-hydraulic performance of PHEs along with technological developments are among the major challenges. The performance of PHEs can be improved by design, fabrication according to design, and the use of nano-fluids. This causes economic problems. However, it can be compensated by improving the performance. In this study, inspired by fish gill shapes, fish gill grooves are designed on the plate surface of a PHE. This is a compact PHE that can be produced by additive manufacturing. It is compared to the performance of commercial Chevron angled PHE to verify the performance improvement under the same conditions. In addition, 0.5 vol% and 1 vol% concentrations of Cu and Al2O3 nanoparticle and water mixtures in hot and cold flow sides are used to increase the heat transfer according to the pressure drop of the fish-gill embossed PHE. The results of the study show that for water and 0.5 vol% Cu/water, its heat transfer rates are respectively 17.5% and 41% higher compared to the Chevron angled PHE. According to water usage in the fish-gill embossed PHE, the use of 0.5 vol% Cu/water nanofluid increases the heat transfer rate by 19.9% and the effectiveness by 24.5%. The narrow flow channels of the fins added to the plate surface cause an increase in the pressure drop of the fish-gill embossed PHE. As a result, nanofluid can be used to reduce the pressure drop compared to water usage. (C) 2022 Elsevier Ltd. All rights reserved.