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SrTiO3 oxygen sensor were fabricated from synthesized SrTiO3 and commercial SrTiO3 using high-energy ball milling and the thick-film screen-printing techniques. The particle sizes, microstructural properties and oxygen sensing properties of the synthesized nano-structured SrTiO3 oxygen sensor were characterized using X-ray diffraction (XRD) and gas sensing measurements. Experimental results showed that particle size of the powders were milled down to be around 20 nm. The effect of different annealing temperatures (400, 500, 600, 700 and 800°C) on the gas sensing properties of the synthesized SrTiO3 sensor to 20% oxygen was characterized. The commercial SrTiO3 (with milling 0 hours and 120 hours) devices, annealed at 400°C, were used as reference. The optimal relative resistance (Rnitrogen/Poxygen) value of 6.35 is obtained for the synthesized SrTiO3 sample annealed at 400°C and operating at 40°C. This operating temperature is much lower than that of the normal low temperature metal oxide semiconducting oxygen gas sensors(300-500°C) and SrTiO3 oxygen gas sensors (>700°C). The response and recovery times are 1.6 minutes and 5 minutes respectively. This is considered fast for near-room temperature operated sensor device. The detected range is 1-20% oxygen. This is a very wide range possible for a single type of sensor material.