MgB2 superconductor sample co-doped with nano-carbon (n-C) and nano-silica (n-SiO2) is prepared and its structural and superconducting properties are compared with pure and n-C and nano SiC (n-SiC) mono-doped samples. Shrinkage of a-lattice parameter is observed for all doped samples, among which the co-doped sample exhibits the maximum shrinkage, an evidence of effective carbon substitution at boron sites. All doped samples show significantly enhanced in-field critical current density J(C)(H), where the co-doped sample dominates others throughout the whole range of field studied. Lattice strains induced by carbon substitution and flux pinning caused by uniformly distributed nano sized Mg2Si particles formed by the reaction between Mg and n-SiO2, are the main reasons for the highly enhanced J(C)(H) behavior of the co-doped superconductor. (C) 2014 Elsevier B.V. All rights reserved.