The current work investigates the performance of petroleum coke (PC) as a blended fuel under pulverized-fuel combustion conditions. Three full-scale combustion experiments were carried out: a pure Carboniferous, high volatile bituminous coal and two blends of this coal with different proportions of PC. The samples studied included feed fuels and blends, fly ashes, chars taken at different positions of the combustion chamber, and chars prepared in a drop tube reactor to test the performance of the individual fuels. The addition of PC led to a substantial increase in the unburned carbon of the fly ashes. The petrographic analysis of the granulometric fractions of the fuels revealed that this increase cannot be attributed to an enrichment in coke of the coarser fractions, as reported in the literature. On the contrary, the finer fraction contained slightly more coke than the raw blend. The petrographic analysis of the chars collected with the suction probe and the fly ashes showed that the two blended fuels were strongly enriched in PC-derived material, indicating a poorer combustibility compared to the high volatile bituminous coal. It is concluded that the reactivity of the blends in the later stages of combustion is related with the contents of PC-derived chars and the burnout itself.