In this work, synthesis and phase stability of a novel dual-phase (HCP–BCC) AlCoTiZn high-entropy alloy are presented. Microstructural evolution and thermal stability of the alloy powder were studied up to their melting point. X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, atomic emission spectrophotometry analysis and hardness measurements were used for the characterization of the HEA. As-milled and the bulk samples consist of an HCP and Co-rich BCC dual phases. The samples heat-treated at intermediate temperatures show HCP and Co-rich two FCC phases. Thermal stability studies reveal that vaporization of Zn occurs at around 800 °C. An extraordinary hardness of 1005 ± 50 HV was observed in the bulk sample. This is mainly attributed to the presence of dual-phase HCP–BCC structures. © 2022, ASM International.