Abstract In the present paper, we report a green synthesis of CrFe2O4 nanoparticles using Cucumis sativus peel extract as a natural surfactant. The coprecipitation route was explored to produce CrFe2O4 nanoparticles by varying Cucumis sativus peel extract composition. The CrFe2O4 nanoparticles were characterized by means of X-ray diffractometer, scanning electron microscope, and Fourier-transform infrared spectroscopy. The results of X-ray diffraction data analysis indicated that the change in the diffraction peak to the higher position of 2θ was influenced by Cucumis sativus peel extract composition. All samples constructed spinel structure in a single phase without any impurity. The scanning electron microscope images showed that the samples had particle size in the nanometric scale and tended to form a spherical shape. In general, the particle size and morphology of the particles were contributed by Cucumis sativus peel extract composition. The absorption bands for atomic bonds of O–H were detected at the wavenumber of 1379, 1614, and 3400–3479 cm−1, while C–H bonds were recorded at the wavenumber of 3000–3400 cm−1. Furthermore, Fe–O and Cr–O bonds appeared at the wavenumber of 430–669 cm−1. Therefore, natural surfactant obtained from Cucumis sativus peel extract in this work becomes a new potential candidate to produce magnetic nanoparticles in large scale production.