We report a correlation between structural phase stability and magnetic properties of Co 2 FeO 4 spinel oxide. We employed mechanical alloying and subsequent annealing to obtain the desired samples. The particle size of the samples changes from 25nm to 45nm. The structural phase separation of samples, except sample annealed at 900°C, into Co-rich and Fe-rich spinel phase has been examined from XRD spectrum, SEM picture, along with EDX spectrum, and magnetic measurements. The present study indicated the ferrimagnetic character of Co 2 FeO 4 , irrespective of structural phase stability. The observation of mixed ferrimagnetic phases, associated with two Curie temperatures at T C1 and T C2 (>T C1 ), respectively, provides the additional support of the splitting of single cubic spinel phase in Co 2 FeO 4 spinel oxide.