Studies on the potential applications of nanoparticles (NPs) synthesized by biological methods attract the attention of researchers. First time in this study, photocatalytic activities of NiFe2O4 NPs synthesized with pomegranate fruit peel extract were determined against brilliant blue. Surface charge and dynamic size of NPs were detected at −11 mV, and 405 nm, respectively. According to scanning electron microscopy images, NiFe2O4 NPs have spherical morphology with a diameter of 75 nm. Energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used for the determination of elemental composition, crystallinity, and functional groups of NPs, respectively. As a result, it was determined that NiFe2O4 NPs were effective for remediation (65%, for 3 h) of dye. The catalytic activity of NiFe2O4 NPs refers to the Fenton mechanism.