We report the synthesis of Mn doped nickel ferrite having the generic formula Ni1-xMnxFe2O4 (x = 0.05, 0.10, 0.15) through chemical co-precipitation technique. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, dc magnetization studies and Mössbauer spectroscopy. XRD measurements showed the formation of pure spinel phase with particle size homogeneity. Rietveld refinement of the diffraction patterns using GSAS showed the presence of cationic vacancies in the sample. The analysis of the Williamson-Hall plot indicated the presence of strain in all the samples. Raman spectroscopy indicated the coexistence of an additional tetragonal phase P4122 in addition to the cubic phase Fd3¯m in the samples. Dc magnetization studies showed the sample possessed negligible coercivity coupled with ferrimagnetic nature, corroborated by the Mössbauer measurement. The Mössbauer studies gave evidence of distortion in the crystal structure due to the dopant ions and the presence of cationic vacancies. The samples possessing low magnetocrystalline anisotropy along with ferrimagnetic behavior are a potential candidate for biomedical industries. •Rietveld analysis of the XRD patterns showed the presence of single spinel phase.•The samples possess low magnetocrystalline anisotropy at a particle size of 50 nm.•SQUID and Mössbauer spectroscopy verified the ferrimagnetic nature of the sample.•Raman spectra showed coexistence of cubic and tetragonal phases in the samples.•The increase in Mn concentration, transforms ferrite from mixed to inverse spinel.