Abstract: Nanoparticles of potassium ferrite (KFeO₂) in this work were synthesized by a simple egg white solution method upon calcination in air at 773, 873, and 973 K for 2 h. The effects of calcination temperature on the structural and magnetic properties of the synthesized KFeO₂ nanoparticles were investigated. By varying the calcination temperature, X-ray diffraction and transmission electron microscopy results indicated the changes in crystallinity and morphology including particle size, respectively. Notably, the reduction in particle size of the synthesized KFeO₂ was found to have a remarkable influence on the magnetic properties. At room temperature, the synthesized KFeO₂ nanoparticles prepared at 873 K exhibited the highest saturation magnetization (M_S) of 2.07 × 10⁴ A·m⁻¹. In addition, the coercivity (H_C) increased from 3.51 to 16.89 kA·m⁻¹ as the calcination temperature increased to 973 K. The zero-field cooled (ZFC) results showed that the blocking temperatures (T_B) of about 125 and 85 K were observed in the samples calcined at 773 and 873 K, respectively. Therefore, this work showed that the egg white solution method is simple, cost effective, and environmentally friendly for the preparation of KFeO₂ nanoparticles.