Abstract: Delafossite AgFeO₂ nanoparticles with a mixture of 2H and 3R phases were successfully fabricated by using a simple co-precipitation method. The resulting precursor was calcined at temperatures of 100, 200, 300, 400, and 500°C to obtain the delafossite AgFeO₂ phase. The morphology and microstructure of the prepared AgFeO₂ samples were characterized by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N₂ adsorption/desorption, X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS) techniques. A three-electrode system was employed to investigate the electrochemical properties of the delafossite AgFeO₂ nanoparticles in a 3 M KOH electrolyte. The delafossite AgFeO₂ nanoparticles calcined at 100°C (AFO100) exhibited the highest surface area of 28.02 m²∙g⁻¹ and outstanding electrochemical performance with specific capacitances of 229.71 F∙g⁻¹ at a current density of 1 A∙g⁻¹ and 358.32 F∙g⁻¹ at a scan rate of 2 mV∙s⁻¹. This sample also demonstrated the capacitance retention of 82.99% after 1000 charge/discharge cycles, along with superior specific power and specific energy values of 797.46 W∙kg⁻¹ and 72.74 Wh∙kg⁻¹, respectively. These findings indicate that delafossite AgFeO₂ has great potential as an electrode material for supercapacitor applications.