In this paper, the authors present a fabrication method of ZnS/ZnO heterostructured nanorods by thermal evaporation ZnS powder on Si/SiO2 substrate, combined with post thermal oxidation process in oxygen gas environment at different temperatures. The obtained products are nanorods with diameters from 200-400 nm and lengths upto several tens of micrometets. X-ray diffraction measurements on the as-received samples disclosed the existence of both the ZnS and ZnO phase in the sample though the ZnS is the major phase. Low temperature (10 K) photoluminescence spectrum showed an emission band in the UV from 320-400 nm with peaks at 334, 376 nm characterizing for Near - Band - Egde (NBE) emission of ZnS and ZnO phases, respectively, and a broad emission band in the visible region peaking at 500 nm related to defect-emission in ZnS, ZnO. Moreover, the low temperature PL of the nanorods after oxidation at 500°C revealed a new emission band locating in between the NBE emissions of the ZnO and ZnS phase at around 358 nm which can be explained as due to the formation of ZnS/ZnO heterostrutures in the sample. The mechanism of formation of ZnS/ZnO heterostructured nanorods and ZnS to ZnO phase transition process under the effect of thermal oxidation will also be discussed.