The structural and magnetic properties of bulk polycrystalline CoFe 2O4 and niobium substituted Co1.1Fe 1.85Nb0.05O4 prepared by solid state reaction method, are presented in this paper. The lattice parameter of Co 1.1Fe1.85Nb0.05O4 is seen to be more than that of CoFe2O4. Saturation magnetization, first order magnetocrystalline anisotropy constant calculated using law of approach to saturation and magnetostriction of Co1.1Fe1.85Nb 0.05O4 are seen to be less than those of CoFe 2O4. Longitudinal magnetostriction of Co 1.1Fe1.85Nb0.05O4 measured at room temperature is -123 × 10-6 at a field of 2.2 kOe, with enhanced strain derivative. Field induced trigonal distortion was observed at 2.2 kOe in Co1.1Fe1.85Nb0.05O4 from the analysis of powder XRD patterns. Co1.1Fe1.85Nb 0.05O4 exhibits ferroelectric and magnetoelectric properties. © 2014 Elsevier B.V. All rights reserved.