Spray pyrolysis is one of the most cost-effective methods to prepare SnO2 films due to its ability to deposit large uniform area, low fabrication cost, simplicity and low deposition temperature. Conventionally, scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) are routinely used to investigate microstructure and crystal structure of the SnO2 films. In the present study, the SnO2 films were deposited by spray pyrolysis at 300, 400 and 500°C and the microstructure of the 500°C film was further examined by using transmission electron microscopy (TEM) and convergent beam electron diffraction (CBED). It was found that large grain-size vertically-aligned columnar SnO2 grains were formed after a few layers of small grain-size randomly oriented SnO2 grains. Moreover, CBED showed the presence of SnO nanodefects that had not been reported before and could not be detected by SEM or XRD.