Pyrolysis is a thermal process where organic materials such as biomass and oil are decomposed and lighter materials such as gas, vapor, liquid products, and char are produced. The aim of this study was to investigate the pyrolysis behavior of sewage sludge in different operating conditions. Using a fixed bed, the influence of some important parameters such as pyrolysis temperature, heating rate, particle size, and N-2 flow rate on product yields was studied. Results showed that with increase in temperature from 400 to 700 degrees C, the char yield decreased from 30.1 to 7.50%, while the gas yield increased from 35.8 to 52.4%. The gas yield also increased from 46.9 to 49.1% as the heating rate increased from 20 to 60 degrees C/s, while the oil yield increased from 45.2 to 46.8% as heating rate increased to 40 degrees C/s and then the increase leveled off.