Heater, known as a furnace or fired heater is used to heat the oil which flows through tubes around a flame. When the tubes are failed, the fired heater reliability is affected. This paper investigates the probable cause/ causes of the radiant tube failure in the fired heater. In that context, depth analysis is conducted as part of the investigative studies, involve visual observation and dimensional measurement, metallographic examination, and chemical analysis. Finally, it has been concluded that the tube radiant has mainly failed due to crevice corrosion. In the other side, spherodization and external corrosion are also found as other failure contributors.