Influence of manganese substitution on the magnetoimpedance ratio and magnetostrictive constant of cobalt ferrite samples has been studied in the present investigation. Magnetoimpedance was found to vary with manganese content and frequency under the action of applied axial magnetic field. Maximum value of magnetoimpedance ratio was obtained for the composition Co 1.1 Mn 0.1 Fe 1.8 O 4 at a low frequency of 10 2 Hz. In order to understand magnetoimpedance behavior of the samples Cole–Cole plot of Mn substituted cobalt ferrites was studied. It was also noted that magnetostrictive constant under applied dc magnetic field changes with manganese content. The magnetic field required for maximum magnetostriction decreases with substitution of cobalt by manganese in Co 1.2−x Mn x Fe 1.8 O 4 . The strain sensitivity ratio dλ/dH was maximum for Co 1.1 Mn 0.1 Fe 1.8 O 4 , whereas value of magnetostriction was maximum for CoMn 0.2 Fe 1.8 O 4 sample.