Urbanization and industrialization have significantly increased the demand for energy, predominantly sourced from nonrenewable fossil fuels such as natural gas, coal, and oil. Biomass-based biofuel has been considered as a suitable and sustainable option to suffice the growing needs. Among several biomass conversion pathways, thermochemical route through pyrolysis has received a lot of attention due to a good yield of liquid bio-oil and the direct conversion of biomass to value-added chemicals. This chapter describes the compositional structure of biomass and compares the physical, chemical, biochemical, and thermochemical techniques used for biomass conversion into useful products. The thermochemical pyrolysis process and the liquid bio-oil obtained as product are discussed to analyze its closeness in terms of compatibility with conventional fuel. Though pyrolytic bio-oil is produced in sufficient quantity, it is not suitable to replace the available nonrenewable energy resources due to the presence of high oxygen functionalities. Therefore, upgradation of this bio-oil is necessary to meet commercial needs and replace conventional energy sources. Various pyrolysis oil upgrading methods to produce high-quality fuel and chemicals with special emphasis on the hydrodeoxygenation reaction are discussed here. This chapter provides a special emphasis on the hierarchical zeolites, which are found to be promising catalysts due to their lesser deactivation and high reaction rate as compared with commercial zeolites.@en