A series of MgCuZn ferrites with generic formula Mg0.5-xCuxZn0.5Fe2O4 where x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 are synthesized by conventional double sintering technique. X-ray diffraction studies have revealed single phase spinal structure. The series of samples are investigated for thermo emf in the temperature range of 40°C to 400°C at an interval of 5°C with 10°C temperature gradient across the sample. From these measurements Seebeck coefficient α and corresponding Fermi energies are calculated for all the samples throughout the investigated temperature region. The compositional variation of Seebeck coefficient at room temperature showed a maximum at x = 0.1 copper concentration. All the samples studied have attained a maximum Seebeck coefficient at certain temperature. All the samples studied have exhibited negative Seebeck coefficient in the entire temperature region of investigation suggesting that these MgCuZn ferrites come under n- type semiconductors.