Co1+xSixFe2 − 2xO4 ferrite system has been studied to estimate the influence of Si and Co substitutions together on the magnetic and magnetostrictive properties. The samples were prepared by standard double sintering ceramic technique. X-ray diffraction patterns of the study confirm spinel crystal structures. Hysteresis and magnetostriction measurements were made on all the samples at room temperature. Mössbauer spectra were also made both at 300 K and at 4 K under the applied field of 5 T in the direction of gamma ray. Nominal decreases in Curie temperature and saturation magnetization were observed. The strain derivative, which relates to stress sensitivity, is observed to increase from 1.13 × 10−9 to 2.51 × 10−9 Å−1 m for x = 0.2 silicon concentration. The variations are explained on the basis of the strength of the exchange interactions between cations, and anisotropy modifications induced by migration of cobalt ions. The results demonstrate the possibility of controlling the magnetic and magnetomechanical properties through Co and Si substitutions.