The production of tin oxide (SnO2) microrods on iridium (Ir)-coated substrates was achieved through the thermal evaporation of Sn powders in which a sufficiently high O2 partial pressure was employed. Scanning electron microscopy revealed that the product consisted of microrods with diameters that ranged from 0.9 to 40 μm. X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction indicated that the microrods were SnO2 with a rutile structure. As the microrod tips were free of metal particles, it was determined that the growth of SnO2 microrods via the present route was dominated by a vapor-solid mechanism. The thickening of rod-like structures was related to the utilization of sufficiently high O2 partial pressure during the synthesis process, whereas low O2 partial pressure facilitated the production of thin rods.