Thin films of molybdenum doped (2.7 at.%) zinc oxide (MZO) were deposited on glass substrates held at room temperature by RF magnetron sputtering of mosaic target of Mo-Zn at different substrate bias voltages. The influence of substrate bias voltage on the structural, electrical and optical properties was investigated. The MZO films deposited on unbiased substrate were of amorphous, while those formed at substrate bias voltage of -40 V and above were of nanocrystalline. The crystallite size of the films improved with the applied bias voltage. At higher substrate bias voltage of -120 V the ion bombardment induced the high defect density in the films hence decrease in the crystallinity. The films formed at substrate bias voltage of -80 V exhibited low electrical resistivity of 1.2x10 -2 â„¦cm and optical transmittance of about 79 %. These films showed optical band gap of 3.29 eV and figure of merit of 19 Ω -1 cm -1 .