The effect of fuel temperature on the spray characteristics of Jet A-1 aviation fuel at various injection pressures discharged from a pressure swirl atomizer was studied. A two-dimensional phase Doppler anemometry system was employed to measure droplet size, and a laser sheet imaging system was used for taking high-quality spray images. The properties of Jet A-1 aviation fuel, especially the viscosity, showed a large variation according to the fuel temperature. The optical measurement results showed that the atomization characteristics vary significantly depending on the fuel temperature, particularly in the low-temperature region. The spray structure was unstable and not able to be developed at low temperature and low pressure. It was found that the currently available correlations to predict the Sauter mean diameter of pressure swirl nozzles were deficient in providing good agreement with the experimental data when the fuel temperature is altered. The viscosity in these models was then written as a second-order polynomial, and good agreement with the experimental data was achieved.