Catalytic upgrading was applied to the liquid product obtained from biomass fast pyrolysis (raw bio-oil) in a continuous reaction system by using dolomite as a low-cost catalyst. The upgrading reactor operates at atmospheric pressure without external H-2 supply and consists of a thermal treatment section, where pyrolytic lignin is deposited, and a catalytic upgrading section, where the thermally treated oil is valorized in-line. The reaction products, i.e., solid (pyrolytic lignin), gases, and upgraded oil, are collected separately after each reaction. The effect that temperature (400700 degrees C) and time on stream (up to 4 h) have on the yield and composition of the products obtained was analyzed for a space-time of 2.4 g(dolomite) h/gfeed. The dolomite effectively reduced the O/C ratio and removed the carboxylic acids and sugars (mainly levoglucosan) contained in the bio-oil. A gaseous product interesting as a fuel and as raw material for syngas production was obtained below 600 degrees C, provided that dolomite is not saturated (efficient CO2 capture). Thus, for reaction times of approximate to 2 h the concentration values in the 400500 degrees C range are H-2 (512%), CO (4838%), CO2 (2.23.2%), and CH4 (2331%). A good deoxygenation level (approximate to 70%) was achieved after 0.5 h reaction at 600 degrees C, yielding oil with the O/C ratio approximate to 0.25 and composed of acetone (22%), phenol (51%), and alkyl-substituted phenols (22%). Upgraded oil with low O/C ratio (approximate to 0.21) and high contents of phenol (86.4%) and alkyl-phenols (5.3%) was obtained after 4 h of reaction at 700 degrees C. This oil has a promising potential for use in phenolic resins formulation and diesel fuel blending.