Combustion characteristics and pollutant emissions of burning fast pyrolysis bio-oil/heavy fuel oil (HFO) blends in a 300-kWth furnace are investigated. Lauan (shorea) wood is used as biomass feedstock for making bio-oil via a fast pyrolysis process. The bio-oil has high viscosity, high water and oxygen content, as well as a low heating value. A furnace test is conducted for pure HFO and bio-oil/HFO blends with various mixing ratios. The results show that instability occurs during the test for cases with more than 5% bio-oil in the emulsion. Notably, it is verified that burning a bio-oil/HFO blend with a 2.5% bio-oil and a 97.5% HFO exhibits similar furnace performance and has lower NO and SO2 emission levels as compared to burning pure HFO. The reductions of NO and SO2 emissions are 2.6% and 7.9% for this blend, respectively.