Electrical transport properties of CdO-ZnO thin film heterostructure have been studied in this work. Highly conducting CdO thin film is deposited on glass substrate by radio frequency magnetron sputtering technique. ZnO thin film was deposited by employing the same technique on CdO coated glass substrate to prepare an isotype heterostructure of these two n-type metal oxide semiconductors. The CdO thin film was of very high electrical conductivity induced by oxygen deficient point defects. The films were characterized by X-ray diffraction measurements, X-ray photoelectron spectroscopic measurements, field emission scanning electron microscopic measurements and electrical conductivity measurements. Carrier diffusion and carrier tunneling through the interface potential lead to an outstanding conducting channel at the ZnO layer of the isotype thin film heterostructure modifying the band structure at the interface.