Sol-gel ZrO2 thin films deposited by dip-coating on various substrates are characterized. The film thickness, the refractive index and the thermo-optic coefficient (δn/δT) are measured using the prism coupler technique. The thickness of the uniform and good quality sol-gel films ranges between 100nm and 130nm, while the refractive index ranges between 1.9 and 2.1 at 25°C, depending on the substrate material and surface quality, and depending on some process parameters. The δn/δT measurements of the sol-gel ZrO2 thin films deposited on several substrates show that the TM refractive index always exhibits much higher dependence with respect to temperature than the TE refractive index. Such variations had not previously been reported and will require much attention and future study due to the importance of δn/δT for advanced optical telecommunications devices.