In recent years, the mandate for CO2 reduction and clean power generation has led to the advancement of research in high-pressure combustion and gasification. Traditionally, thermocouples monitor the wall temperature of a gasifier, and gas analyzers record the composition of the syngas produced. This paper describes flame emission spectroscopic measurements performed in a pilot-scale entrained-flow gasifier operating at a maximum pressure of 15 bar (g) with petroleum coke as fuel. Low cost and availability make petroleum coke attractive for use in energy production. In the current work, flame spectra observed in the visible region (500-800 nm) during petroleum coke gasification, in the pilot-scale gasifier at CanmetENERGY, are presented. These spectra were acquired with a cooled and purged fiber optic probe coupled to a spectrometer. Gasification flame spectra and information on reaction chamber temperature and the emission peaks of alkali metals and other spectral features observed in these measurements are discussed. The results show that flame emission spectroscopy is useful for gasifier performance monitoring.