MnFe2O4 nanoparticles were synthesised using co-precipitation method and investigated by the techniques such as x-ray diffraction (XRD), field effect scanning electron microscopy (FESEM) and a vibrating sample magnetometer (VSM). The nanoparticles were of an average crystallite size of ~ 20 nm at molarities 7M and 9M of NaOH without annealing / sintering the samples. X-ray diffraction was used to determine the crystallite size, lattice parameter, and density of the nanoparticles. The FESEM images clearly show the production of spherical nanoparticles. Manganese ferrite nanoparticles were found to have the correct stoichiometry, as is evident from energy-dispersive X-ray spectroscopy (EDS). The saturation magnetization, coercivity, retentivity, squareness ratio, dead layer thickness, magnetic moment, and anisotropy constant were estimated using VSM.